Dissecting the Cloud – Part 2

This post further delves in a little more deeply into the cloud. In the last post Dissecting the Cloud –Part1, I described the analogy of a person partitioning a large house by creating self-contained units through the use of a hypervisor which abstracts the underlying hardware( CPU, storage and NICs) into virtual CPUs, virtual NICs and virtual disks.

Hence there are has several instances on the cloud each with its own CPU, NIC and storage. In fact several tenants can reside on the same cloud with their own individual CPU, NIC and storage. This is known as multi-tenancy.

However multi-tenancy creates a unique set of associated issues similar to that of a multi-tenanted house. For e.g. how does one isolate one tenant from another? How does one charge each tenant? Are the tenants secured from the prying eyes of their neighbors? How can the owner ensure that one  particular tenant does not consume an inordinate amount of water or electricity at the expense of other tenants?

These are typical problems in a multi-tenanted cloud. A common and a high profile issue in the cloud is that of the ‘noisy neighbor’. In this situation one of the instances of the cloud hogs the network bandwidth or the storage tier, resulting in a severe bandwidth crunch or storage access problems for other instances. Here is an interesting article on the noisy neighbor issue “The Problem with noisy neighbors in the cloud”.

It appears that IBM has patented a solution for the bandwidth crunch caused by noisy neighbors: IBM patents ‘noisy neighbor’ problem with SDN.

In order to ensure that multi-tenancy can be realized in the cloud it is essential to isolate the virtual CPUs, network and storage in the cloud

Network isolation: Network isolation is achieved through the use of VPNs (virtual private network), VLANs (Virtual LANS) and subnetting.

A VPN creates a secure tunnel between a user and the cloud instance while accessing the instance from the internet. The data in motion is encrypted using IPSec.  Also vNICs belonging to a client are logically grouped together in a VLAN. Groups of vNICs can be sub-netted together to allow broadcast between then.  VLANs can effectively isolate traffic between itself and other VLANs. A very good write-up of VLANs and sub-netting can be seen at “What is the difference between subnetting and VLAN”.

Storage isolation: Storage in cloud can be made of block storage, SAN or NAS storage. Storage isolation is typically achieved through the hypervisor and zoning. Zoning is the partitioning of a Fibre Channel fabric into smaller subsets to restrict interference, add security, and to simplify management.  While a SAN makes available several devices and/or ports to a single device, each system connected to the SAN should only be allowed access to a controlled subset of these devices/ports.

CPU isolation: The hypervisor does create individual instances all fairly isolated from one another. However this is the area that is receiving more attention than storage or networking isolation because of security concerns and is prone to attack. In fact I was greatly surprised to hear that there is a technique called ‘side channel’ attack by which an intruder by just observing the time that is taken for computations and the temperatures generated can reverse engineer the actual instructions. This is really a scary thought!

This is how multi-tenancy is achieved in clouds. I hope to revisit this topic again in the future.

Dissecting the Cloud – Part 1

“The Cloud brings it with it the promise of utility-style computing and the ability to pay according to usage.

Cloud Computing provides elasticity or the ability to grow and shrink based on traffic patterns.

Cloud Computing does away with CAPEX and the need to buy infrastructure upfront and replaces it with OPEX model and so on”.

All this old news and has been repeated many times. But what exactly constitutes cloud computing? What brings about the above features? What are its building blocks of the cloud that enable one to realize the above?

This post tries to look deeper into the innards of the Cloud to determine what the cloud really is.

Before we get to this I would like to dwell on an analogy to understand the Cloud better.

Let us assume, Mr. A owns a large building of about 15,000 sq feet and about 100 feet tall. Let us assume that Mr. A wants to rent this building.

Now, assume that the door of this building opens to single, large room on the inside!

Mr. X comes to rent this building. If this was the case then poor Mr. X would have to pay through his nose, presumably, for the entire building even though his requirement would have been for a small room of about 600 x 600 feet. Imagine the waste of space. Moreover this would also have resulted in an enormous waste of electricity. Imagine the lighting needed. Also an inordinate amount of water would have to be utilized if this single, large room needed to be cleaned. The cost for all of this would have to be borne by Mr. X.

This is clearly not a pleasant state of affairs for either Mr. X or for the owner Mr. A of the building.

The solution to this is easy.  What Mr. A needs to do, is to partition the building into self-contained rooms (600 x 600 sq feet) with all the amenities. Each self-contained unit would need to have its own electricity and water meter.

Now Mr. A can rent rooms to different tenants on their need basis. This is a win-win situation both for Mr, A and Mr. X. The tenants only need to pay for the rooms they occupy and the electricity and water they consume.

This is exactly the principle behind cloud computing and is known as ‘virtualization’

There are 3 computing components that one must consider. CPU, Network and Storage. The below picture shows the virtualization of CPU,RAM, NIC (network card), Disk (storage)

The Cloud is essentially made up of  anywhere between 100 servers to 100,000 servers. The servers are akin to the large building. Running a single OS and application(s) on the entire server is a waste of computing, storage and network resources.

Virtualization abstracts the hardware, storage and network through the use of software known as the ‘hypervisor’. On top of the hypervisor several ‘guest OSes’ can run. Applications can then run on these guest OSes.

Hence over the CPU (single, dual or multi-core) of the server,  multiple guest OS’es  can run each with its own set of applications

This is similar to partitioning the large CPU resource of the server into smaller units.

There are 3 main Virtualization technologies namely VMware, Citrix and MS Hyper-V

Here is a diagram showing the 3 main the virtualization technologies

To be continued ...

Close encounters with the future

Published in Telecom Asia, Oct 22,2013 - Close encounters with the future

Where a calculator on the ENIAC is equipped with 18,000 vacuum tubes and weighs 30 tons, computers in the future may have only 1,000 vacuum tubes and perhaps weigh 1.5 tons.—POPULAR MECHANICS, 1949

Introduction: Ray Kurzweil in his non-fiction book “The Singularity is near – When humans transcend biology” predicts that by the year 2045 the Singularity will allow humans to transcend our ‘frail biological bodies’ and our ‘petty, derivative and circumscribed brains’ . Specifically the book claims “that there will be a ‘technological singularity’ in the year 2045, a point where progress is so rapid it outstrips humans' ability to comprehend it. Irreversibly transformed, people will augment their minds and bodies with genetic alterations, nanotechnology, and artificial intelligence”.

He believes that advances in robotics, AI, nanotechnology and genetics will grow exponentially and will lead us into a future realm of intelligence that will far exceed biological intelligence. This explosion will be the result of ‘accelerating returns from significant advances in technology”

Futurescape

Here is a look at some of the more fascinating key trends in technology. You can decide whether we are heading to Singularity or not.

Autonomous Vehicles (AVs): Self driving cars have moved from the realm of science fiction to reality in recent times. Google’s autonomous cars has already driven around half a million miles. All the major car manufacturers of the world from BMW, Mercedes, Toyota, Nissan, Ford or GM are all coming with their own versions of autonomous cars. These cars are equipped with Adaptive Cruise Control and Collision Avoidance technologies and are already taking away control drivers. Moreover AVs alert drivers, if their attention strays from the road ahead, for too long. Autonomous Vehicles work with the help of Vehicular Communication Technology.

Vehicular Communication along with the Intelligent Transport Systems (ITS) achieves safety by enabling communication between vehicles, people and roads. Vehicle-to-vehicle communications are the fundamental building block of autonomous, self-driving cars. It enables the exchange of data between vehicles and allows automobiles to "see" and adapt to driving obstacles more completely, preventing accidents besides resulting in more efficient driving.

Smart Assistants: From the defeat of Kasparov in chess by IBM’s Deep Blue in 1997, and then subsequently to  the resounding victory of IBM’s Watson in Jeopardy, capable of understanding natural human language, to the more prevalent Apple’s intelligent assistant Siri, Artificially Intelligent  (AI) systems have come a long way. The newest trend in this area is Smart Assistants.  Robots are currently analyzing documents, filling prescriptions, and handling other tasks that were once exclusively done by humans. Smart Assistants are already taking over the tasks of BPO operators, paralegals, store clerks, baby sitters. Robots, in many ways, are not only smarter than humans, but also do not get easily bored,

Intelligent homes and intelligent offices. Rapid advances in technology will be closer to the home both literally and figuratively. The future home will have the ability to detect the presence of people, pets, smoke and changes to humidity, moisture, lighting, temperature. Smart devices will monitor the environment and take appropriate steps to save energy, improve safety and enhance security of homes.  Devices will start learning your habits and enhance your comfort and convenience. Everything from thermostats, fire detectors, washing machines, refrigerators will be equipped electronics that will be capable of adapting to the environment. All gadgets at home will be accessible through laptops, tablets or smartphones from anywhere. We will be able to monitor all aspects of our intelligent home from anywhere.

Smart devices will also make major inroads into offices leading to the birth of intelligent offices where the lighting, heating, cooling will be based on the presence of people in the offices. This will result in an enormous savings in energy. The advances in intelligent homes and intelligent offices will be in the greater context of the Smart Grid.

Swarms of drones: Contrary to the use of weaponized drones for unmanned aerial survey of enemy territory we will soon have commercial drones. Drone will start being used for civilian purposes.  The most compelling aspect of drones these days is the fact that they can be easily manufactured in large quantities, are cheap and can perform complex tasks either singly or collectively. Remotely controlled drones can perform hundreds of civilian jobs, including traffic monitoring, aerial surveying, and oil pipeline inspections and monitoring of crop conditions. Drones are also being employed for conservation of wildlife. In the wilderness of Africa, drones are already helping in providing aerial footage of the landscape, tracking poachers and in also herding elephants. However, before drones become a common sight, it is necessary to ensure that appropriate laws are made for maintaining the safety and security of civilians. This is likely to happen in US in 2015, when the Federal Aviation Administration (FAA) will come up with rules to safely integrate drones into the American skies.

MOOC (Massive Online Open Course): The concept of MOOC, or the ‘Massive Open Online Course’ from top colleges, though just a few years old, is already taking the world by storm. Coursera, edX and Udacity are the top 3 MOOCs besides many others and offer a variety of courses on technology, philosophy, sociology, computer science etc.  As more courses are available online, the requirements of having a uniform start and end date will diminish gradually. The availability of course lectures at all times and through all devices, namely the laptop, tablet or smartphone, will result in large scale adoption by students of all ages.

Contrary to regimented classes MOOCs now allow students to take classes at their own pace. It is likely that some students will breeze through an entire semester worth of classes in a few weeks. It is also likely that a few students will graduate in 4 years with more than a couple of degrees. MOOCs are a natural development considering that the world is going to be more knowledge driven where there will be the need for experts with a diverse set of in-depth skills. Here is an interesting article in WSJ “What College will be like in 2023”

3D Printing: This is another technology that is bound to become ubiquitous in our future. 3D printers will revolutionize manufacturing in ways we could never imagine. A 3-D printer is similar to a hot-glue gun attached to a robotic arm. A 3-D printer creates an object by stacking one layer of material, typically plastic or metal, on top of another.  3D printers have been used for making everything from prosthetic limbs, phone cases, lamps all the way to a NASA funded 3D pizza. Here is a great article in New York Times “Dinner is Printed” It is likely that a 3D printer would be indispensable to our future homes much like the refrigerator and microwave.

Artificial sense organs: A recent news items in Science 2.0 “The Future touch sensitive prosthetic limbs”   discusses the invention of a prosthetic limb that can actually provide the sense of touch by stimulating the regions of the brain that deal with the sense of touch. The researchers identified the neural activity that occurs when grasping or feeling an object and successfully induced these patterns in the brain. Two parallel efforts are underway to understand how the human brain works. They are “The Human Brain Project” which has 130 members of the European Union and Obama’s BRAIN project. Both these projects attempt to ‘to give us a deeper and more meaningful understanding of how the human brain operates”. Possibilities as in the movies ‘Avatar’ or ‘Terminator’ may not be far away.

The Others: Besides the above, technologies like Big Data, Cloud Computing, Semantic Web, Internet of Things and Smart Grid will also be swamp us in the future and much has already been said about it.

Conclusion: The above sets of technologies represent seismic shifts and are bound to explode in our future in a million ways.

Given the advances in bionic limbs, Machine Intelligent AI systems, MOOCs, Autonomous Vehicles are we on target for the Singularity?

I wouldn’t be surprised at all!

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‘The Search’ is not yet over!

Published in Telecom Asia, Oc9, 2013 - 'The search' is not yet over!
In this post I take a look at the technologies that power the now indispensable and ubiquitous ‘search’ that we do over the web. It would be  easy to rewind the world by at least 3 decades by simply removing ‘the search’ from our lives.
A classic article in the New York Times, ‘The Twitter trap’ discusses how technology is slowly replacing some of our more common faculties like the ability to memorize or perform simple calculations mentally.
For e.g. until the 15^th century people had to remember a lot of information. Then came Gutenberg with his landmark invention, the printing press, which did away with the need to store information. Closer to the 2oth century the ‘Google Search’ now obviates the need to remember facts about anything. Detailed information is just a mouse click away.
Here’s a closer look at evolution of search technologies
The Inverted Index: The inverted index is a way to search the existence of key words or phrases in documents.  The inverted index is an index data structure storing a mapping from content, such as words or numbers, to its locations in a document or a set of documents. The ability to store words and the documents in which it is present, allows for an quick  retrieval of the related documents in which the word(s) are present. Search engines like Google, Bing or Yahoo typically crawl of the web continuously and keep updating this index of words versus the documents as new web pages and web sites are added. The inverted index is a simplistic method and is neither accurate nor efficient.

Google’s Page Rank: As mentioned before merely the presence of words in documents alone is not sufficient to return good search results. So Google came along with its PageRank algorithm. PageRank is an algorithm used by the Google’s  web search engine to rank websites in their search engine results.  According to Google PageRank works by “counting the number and quality of links to a page to determine a rough estimate of how important the website is.”  The underlying assumption is that more important websites are likely to receive more links from other websites.
In essence the PageRank algorithm tries to determine the likelihood that a surfer will land on a particular page by randomly clicking on links. Clearly the PageRank algorithm has been very effective for searches as now ‘googling’ is synonymous to searching (see below from Wikipedia)

Graph database: While the ‘Google Search’ is extremely powerful it would make more sense if the search could be precisely tailored to what the user is trying to search. A typical Google search throws up a few 100 million results.  This has led to even more powerful techniques, one of which is the ‘Graph database’. In a Graph database data is represented as a graph. Nodes in the graph can be entities and edges could be relationships. A search on the graph database will result in the traversal of the graph from a specific start node to specific terminating node. Here is a fun representation of a simple Graph database representation from InfoQ

Google has recently come out with its Knowledge Graph which is based on this technology. Facebook allows users to create complex queries of status updates using the graph database.
Finally, what next??
A Cognitive Search??: Even with the graph database the results cannot be very context specific. What I would hope to happen in the future is have a sort of a ‘Cognitive Search’ where the results would be bounded and would take into account the semantics and context of a user specified phrase or request.
So for e.g. if a user specified ‘Events leading to the Iraq war’ the search should throw all results which finally culminated in the Iraq war.
Alternatively if I was interested in knowing for e.g. ‘the impact of iPad on computing’ then the search should throw precise results from  the making of the iPad, the launch of iPad, the various positive and negative reviews and impact iPad has had on the tablet and computing industry as a whole.
Another interesting query would ‘The events that led to the downfall of a particular government in election of 1998’ the search should precisely output all those events that were significant during this specific period.
I would assume that the results themselves would come out as a graph with nodes and edges specifying which event(s) triggered which other event(s) with varying degrees of importance.
However this kind of ability where the search is cognitive is probably several years away!
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Future calls. Visualizing an IMS based future.

Future calls. In case you didn’t notice there is a word play in the previous sentence. I have used the word “calls” both as a verb and as a noun. Clever, right? ;-)

This post takes a closer look at how the future would look like with regard to calls.

Our world is getting more interconnected and more digitized. We view this digitized world through either smartphones, tablets, laptops, smart TV etc. So these days we can browse the web through any of the above devices. Social applications like Facebook. Twitter, LinkedIn or utilities like Evernote and Pocket are equally accessible through any of the devices at any time and at any place.

While we are able to use these devices interchangeably why is that we always receive calls only through phones (mobile or landlines).  Would it be possible to switch calls between these devices?

In fact this is very possible and is included in the vision that IP Multimedia Systems had set for itself. While IMS is yet to take off, it is bound to get traction in the not too distant future.

Assuming that this is going to happen, here is my visualization of how a typical day in the future (possibly 2015/2016) would look like.



Here is an imagined scenario

Akash is joined to a conference call at 8.00 am, while at home. When he answers his smartphone he gets a notification “Nearby devices 1) Laptop2) Tablet 3) TV. Choose device to handover to”.  If he chooses the tablet, laptop or TV the call would be seamlessly transferred to this device.  When the call appears on his tablet, laptop or TV there could be another notification “Do you want to add video to the call? Choose Yes or No” the call would automatically be upgraded to a video call if the far end also has this capability. Lets assume that Akash completes this call.

On his way to the office he receives another call on his mobile. When Akash answers his smartphone he is again notified regarding the devices nearby 1) Laptop 2) Car dashboard. Now Akash can just command his smartphone to receive the call on his car dashboard if he is driving his car. If he is being driven he can handover the call to his laptop. When he receives the call in his laptop he could receive a popup, “Do you want to add video and/or data to this call?” If he chooses to add both video and data he can videoconference while also whiteboarding with his colleagues.

He can then continue the call on his smartphone while walking to his cubicle.

The transition between devices will be seamless.

This handover of calls between devices and also the switching back and forth from voice only to voice, video and data (whiteboarding) is bound to happen in the not too distant future.

So keep you ears and eyes wide open.
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Envisioning a Software Defined IP Multimedia System (SD-IMS)

In my earlier post “Architecting a cloud based IP Multimedia System (IMS)” I had suggested the idea of “cloudifying” the network elements of the IP Multimedia Systems. This would bring multiple benefits to the Service Providers as it would enable quicker deployment of the network elements of the IMS framework, faster ROI and reduction in CAPEX. Besides, the CSPs can take advantage of the elasticity and utility style pricing of the cloud.

This post takes this idea a logical step forward and proposes a Software Defined IP Multimedia System (SD-IMS).

In today’s world of scorching technological pace, static configurations for IT infrastructure, network bandwidth and QOS, and fixed storage volumes will no longer be sufficient.

We are in the age of being able to define requirements dynamically through software. This is the new paradigm in today’s world. Hence we have Software Defined Compute, Software Defined Network, Software Defined Storage and also Software Defined Radio.

This post will demonstrate the need for architecting an IP Multimedia System that uses all the above methodologies to further enable CSPs & Operators to get better returns faster without the headaches of earlier static networks.

IP Multimedia Systems (IMS) is the architectural framework proposed by 3GPP body to establish and maintain multimedia sessions using an all IP network. IMS is a grand vision that is access network agnostic, uses an all IP backbone to begin, manage and release multimedia sessions.

The problem:

Any core network has the problem of dimensioning the various network elements. There is always a fear of either under dimensioning the network and causing failed calls or in over dimensioning resulting in wasted excess capacity.

The IMS was created to handle voice, data and video calls. In addition in the IMS, the SIP User Endpoints can negotiate the media parameters and either move up from voice to video or down from video to voice by adding different encoders.  This requires that the key parameters of the pipe be changed dynamically to handle different QOS, bandwidth requirements dynamically.

The solution

The approach suggested in this post to have a Software Defined IP Multimedia System (SD-IMS) as follows.

In other words the compute instances, network, storage and the frequency need to be managed through software based on the demand.

Software Defined Compute (SDC): The traffic in a Core network can be seasonal, bursty and bandwidth intensive. To be able to handle this changing demands it is necessary that the CSCF instances (P-CSCF, S-CSCF,I-CSCF etc) all scale up or down. This can be done through Software Defined Compute or the process of auto scaling the CSCF instances. The CSCF compute instances will be created or destroyed depending on the traffic traversing the switch.

Software Defined Network (SDN): The IMS envisages the ability to transport voice, data and video besides allowing for media sessions to be negotiated by the SIP user endpoints. Software Defined Networks (SDNs) allow the network resources (routers, switches, hubs) to be virtualized.

SDNs can be made to dynamically route traffic flows based on decisions in real time. The flow of data packets through the network can be controlled in a programmatic manner through the Flow controller using the Openflow protocol. This is very well suited to the IMS architecture. Hence the SDN can allocate flows based on bandwidth, QoS and type of traffic (voice, data or video).

Software Defined Storage (SDS): A key component in the Core Network is the need to be able charge customers. Call Detail Records (CDRs) are generated at various points of the call which are then aggregated and sent to the bill center to generate the customer bill.

Software Defined (SDS) abstracts storage resources and enables pooling, replication, and on-demand provisioning of storage resources. The ability to be able to pool storage resources and allocate based on need is extremely important for the large amounts of data that is generated in Core Networks

Software Defined Radio (SDR): This is another aspect that all Core Networks must adhere to. The advent of mobile broadband has resulted in a mobile data explosion portending a possible spectrum crunch. In order to use the available spectrum efficiently and avoid the spectrum exhaustion Software Define Radio (SDR) has been proposed. SDRs allows the radio stations to hop frequencies enabling the radio stations to use a frequency where this less contention (see We need to think differently about spectrum allocation … now).In the future LTE-Advanced or LTE with CS fallback will have to be designed with SDRs in place.

Conclusion:

A Software Defined IMS makes eminent sense in the light of characteristics of a core network architecture.  Besides ‘cloudifying’ the network elements, the ability to programmatically control the CSCFs, network resources, storage and frequency, will be critical for the IMS. This is a novel idea but well worth a thought!
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A closer look at “Robot Horse on a Trot” in Android

This post is result of my dissatisfaction with the awkward and contrived gait of my Robot Walker in my earlier post "Simulating a Robot Walker” in Android. The movements seemed to be a little too contrived for my comfort so I decided to make a robot which has far more natural movements.

To do this I pondered on what constitutes a walking motion for any living thing. With a little effort it is clear that the following movements occur during walking

Mechanics of leg movements during walking

The upper part of the leg swings upward and downward pivoted at the hip.

The lower part of the leg, pivoted at the knee, swings in the opposite direction to the upper part of the leg. i.e when the upper part swings upward and counter-clockwise, the lower part of the leg swings downward & clockwise which results in the bend at the knees

When one leg goes up, counterclockwise, the other leg goes down or it swing clockwise and vice versa. See figure below

So with these rules it was easy to make the legs.

Frontal leg (first leg)

The upper part of the leg is connected to the Robot Body through a revoluteJoint with a pivot at the body. The upper leg has a motor and swings between an upper and lower limit

// Create upper leg

upperLeg = new Sprite(x, y, this.mLegTextureRegion, this.getVertexBufferObjectManager());

upperLegBody = PhysicsFactory.createBoxBody(this.mPhysicsWorld, upperLeg, BodyType.DynamicBody, LEG_FIXTURE_DEF);

this.mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(upperLeg, upperLegBody, true, true));

this.mScene.attachChild(upperLeg);

//Create an anchor/pivot at the body of the robot

Vector2 anchor1 = new Vector2(x/PIXEL_TO_METER_RATIO_DEFAULT,y/PIXEL_TO_METER_RATIO_DEFAULT);

//Attach upper leg to the body using a revolute joint with a motor

final RevoluteJointDef rJointDef = new RevoluteJointDef();

rJointDef.initialize(upperLegBody, robotBody, anchor1);

rJointDef.enableMotor = true;

rJointDef.enableLimit = true;

rJoint = (RevoluteJoint) this.mPhysicsWorld.createJoint(rJointDef);

rJoint.setMotorSpeed(4);

rJoint.setMaxMotorTorque(15);

//Set upper and lower limits for the swing of the leg

rJoint.setLimits((float)(0 * (Math.PI)/180), (float)(30 * (Math.PI)/180));

//Fire a periodic timer

new IntervalTimer(secs,rJoint);

The lower leg pivoted to the bottom of the upper leg through a revoluteJoint swings in the opposite direction of the upper leg between the reverse angle limts. By the way, I had tried every possible joint between the lower & the upper leg (distanceJoint, weldJoint,prismaticJoint) but the revoluteJoint is clearly the best.

// Create lower leg

lowerLeg= new Sprite(x, (y+50), this.mLegTextureRegion, this.getVertexBufferObjectManager());

lowerLegBody = PhysicsFactory.createBoxBody(this.mPhysicsWorld, lowerLeg, BodyType.DynamicBody, LEG_FIXTURE_DEF);

this.mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(lowerLeg, lowerLegBody, true, true));

this.mScene.attachChild(lowerLeg);

Vector2 anchor2 = new Vector2(x/PIXEL_TO_METER_RATIO_DEFAULT, (y+50)/PIXEL_TO_METER_RATIO_DEFAULT);

//Create a revoluteJoint between upper & lower leg

final RevoluteJointDef rJointDef1 = new RevoluteJointDef();

rJointDef1.initialize(lowerLegBody, upperLegBody, anchor2);

// The lower leg swings in opposite direction to upper leg

rJointDef1.enableMotor = true;

rJointDef1.enableLimit = true;

rJoint1 = (RevoluteJoint) this.mPhysicsWorld.createJoint(rJointDef1);

rJoint1.setMotorSpeed(-4);

rJoint.setMaxMotorTorque(15);

//Set upper and lower limits for the swing of the leg

// Set appropriate limits for lower leg

rJoint1.setLimits((float)(-30 * (Math.PI)/180), (float)(0 * (Math.PI)/180));

new IntervalTimer(secs,rJoint1);

Rear Leg (alternate leg)

Every alternate leg moves in the converse direction as the previous leg

//Create the alternative leg

publicvoid createAltLeg(float x, float y, int secs ){

// Create upper part of leg

upperLeg = new Sprite(x, y, this.mLegTextureRegion, this.getVertexBufferObjectManager());

upperLegBody = PhysicsFactory.createBoxBody(this.mPhysicsWorld, upperLeg, BodyType.DynamicBody, LEG_FIXTURE_DEF);

this.mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(upperLeg, upperLegBody, true, true));

this.mScene.attachChild(upperLeg);

//Create an anchor/pivot at the body of the robot

Vector2 anchor1 = new Vector2(x/PIXEL_TO_METER_RATIO_DEFAULT,y/PIXEL_TO_METER_RATIO_DEFAULT);

//Attach upper leg to the body using a revolute joint with a motor

final RevoluteJointDef rJointDef = new RevoluteJointDef();

rJointDef.initialize(upperLegBody, robotBody, anchor1);

rJointDef.enableMotor = true;

rJointDef.enableLimit = true;

rJoint = (RevoluteJoint) this.mPhysicsWorld.createJoint(rJointDef);

// This leg swings in the opposite direction of the previous leg

rJoint.setMotorSpeed(-4);

rJoint.setMaxMotorTorque(15);

//Set upper and lower limits for the swing of the leg

rJoint.setLimits((float)(0 * (Math.PI)/180), (float)(30 * (Math.PI)/180));

new IntervalTimer(secs,rJoint);

// Create lower leg

lowerLeg= new Sprite(x, (y+50), this.mLegTextureRegion, this.getVertexBufferObjectManager());

lowerLegBody = PhysicsFactory.createBoxBody(this.mPhysicsWorld, lowerLeg, BodyType.DynamicBody, LEG_FIXTURE_DEF);

this.mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(lowerLeg, lowerLegBody, true, true));

this.mScene.attachChild(lowerLeg);

Vector2 anchor2 = new Vector2(x/PIXEL_TO_METER_RATIO_DEFAULT, (y+50)/PIXEL_TO_METER_RATIO_DEFAULT);

//Create a revoluteJoint between upper & lower leg

final RevoluteJointDef rJointDef1 = new RevoluteJointDef();

rJointDef1.initialize(lowerLegBody, upperLegBody, anchor2);

rJointDef1.enableMotor = true;

rJointDef1.enableLimit = true;

rJoint1 = (RevoluteJoint) this.mPhysicsWorld.createJoint(rJointDef1);

//The lower part of the leg has the opposite swing to the upper part

rJoint1.setMotorSpeed(4);

rJoint.setMaxMotorTorque(15);

//Set appropriate upper and lower limits for the swing of the leg

rJoint1.setLimits((float)(-30 * (Math.PI)/180), (float)(0 * (Math.PI)/180));

// Fire a periodic timer

new IntervalTimer(secs,rJoint1);

I attached a horse's head to the body using a WeldJoint

//Create the horse and attach the head using a Weld Joint

horse = new Sprite(140, 320, this.mHorseTextureRegion, this.getVertexBufferObjectManager());

horseBody = PhysicsFactory.createBoxBody(this.mPhysicsWorld, horse, BodyType.DynamicBody, HORSE_FIXTURE_DEF);

this.mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(horse, horseBody, true, true));

this.mScene.attachChild(horse);

Vector2 anchor = new Vector2(140/PIXEL_TO_METER_RATIO_DEFAULT, 320/PIXEL_TO_METER_RATIO_DEFAULT);

final WeldJointDef weldJointDef = new WeldJointDef();

weldJointDef.initialize(horseBody, robotBody, anchor);

this.mPhysicsWorld.createJoint(weldJointDef);

So now I had a horse that was ready to trot or canter around.

You can see the clip at Robot Horse on a canter using Android

The complete code can be cloned at GitHub RobotHorse

Some issues

Here are some issues with the above code

The horse is quite unstable. If I move the phone vertically, the horse tends to tip backwards. The above clip was recorded with the phone lying on a table

The motor speeds, torque and the masses of the different objects have to be adjusted very carefully. If the horse's head or the body is too heavy the legs buckle under the weight

Sometimes when I start the simulation the horse seems to bounce off the floor

I have carefully adjusted the mass, friction, motor speeds etc very carefully. Feel free to play around with them.

Comments & suggestions are welcome.
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“Is it an animal? Is it an insect?” in Android

“Is it an animal? Is it an insect?”. The answer is neither. In fact it is my version of a 'robot walker' in android using Box2D & AndEngine. I got interested in this simulation after I saw the Theo Jansen walker in JBox2D (look under Joints) . I did take a look at the code for this but I found it difficult to follow so I made my own version of a robot walker.

In this connection I would like to point yot to an excellent and a fascinating TED talk by the creator Theo Jansen himself on “My creations, a new form of life”. His creations are really jaw- dropping.

Anyway getting back to my post I thought about what would make the insect walk? After some thought I realized that I had to create a swinging motion of the upper part of the leg combined with the lower leg motion which does not bend that much.

So I created a robot body which is a flat rectangular shape

//Create the robot body

robot = new Sprite(100, 360, this.mRobotTextureRegion, this.getVertexBufferObjectManager());

robotBody = PhysicsFactory.createBoxBody(this.mPhysicsWorld, robot, BodyType.DynamicBody, BODY_FIXTURE_DEF);

this.mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(robot, robotBody, true, true));

this.mScene.attachChild(robot);

Creating legs

Then I create 6 different legs spaced apart

createLeg(100,360,1);

createLeg(120,360,1);

createLeg(140,360,1);

createLeg(160,360,1);

createLeg(180,360,1);

createLeg(200,360,1);

createLeg(220,360,1);

createLeg(240,360,1);

The createLeg() creates an upper and lower part of the leg. The upper part of the leg is connected to the body of the robot through a revoluteJoint as follows

Upper Leg

// Create upper leg

upperLeg = new Sprite(x, y, this.mLegTextureRegion, this.getVertexBufferObjectManager());

upperLegBody = PhysicsFactory.createBoxBody(this.mPhysicsWorld, upperLeg, BodyType.DynamicBody, LEG_FIXTURE_DEF);

this.mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(upperLeg, upperLegBody, true, true));

this.mScene.attachChild(upperLeg);

//Create an anchor/pivot at the body of the robot

Vector2 anchor1 = new Vector2(x/PIXEL_TO_METER_RATIO_DEFAULT,y/PIXEL_TO_METER_RATIO_DEFAULT);

//Attach upper leg to the body using a revolute joint with a motor

final RevoluteJointDef rJointDef = new RevoluteJointDef();

rJointDef.initialize(upperLegBody, robotBody, anchor1);

rJointDef.enableMotor = true;

rJointDef.enableLimit = true;

rJoint = (RevoluteJoint) this.mPhysicsWorld.createJoint(rJointDef);

Lower Leg

The lower leg is connected to upper leg through a distance joint

// Create lower leg

lowerLeg= new Sprite(x, (y+50), this.mLegTextureRegion, this.getVertexBufferObjectManager());

lowerLegBody = PhysicsFactory.createBoxBody(this.mPhysicsWorld, lowerLeg, BodyType.DynamicBody, LEG_FIXTURE_DEF);

this.mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(lowerLeg, lowerLegBody, true, true));

this.mScene.attachChild(lowerLeg);

// Connect the lower and upper leg with distance joint

Vector2 anchor2 = new Vector2(x/PIXEL_TO_METER_RATIO_DEFAULT, (y+50)/PIXEL_TO_METER_RATIO_DEFAULT);

//Create a distanceJoint between upper & lower leg

DistanceJointDef distanceJoint1 = new DistanceJointDef();

distanceJoint1.initialize(upperLegBody,lowerLegBody, anchor2,anchor2);

distanceJoint1.collideConnected = true;

distanceJoint1.dampingRatio = 0.5f;

distanceJoint1.frequencyHz = 10.0f;

this.mPhysicsWorld.createJoint(distanceJoint1);

Creating a walking movement

To create a walking movement I create a timer task which triggers after a delay of 1 second periodically and makes the upper legs's revoluteJoint swing between angles within an upper and lower limit.

new IntervalTimer(secs,rJoint);

The timer itself reverses the motor every time it fires

class RemindTask extends TimerTask {

RevoluteJoint rj1;;

RemindTask(RevoluteJoint rj){

rj1 = rj;

}

@Override

publicvoid run() {

reverseMotor();

}

publicvoid reverseMotor(){

rj1.setMotorSpeed(-(rj1.getMotorSpeed()));

rj1.setMaxMotorTorque(10);

}

}

With the above the robot walker is able to walk awkwardly as seen in the video

Robot Walker in Android

The entire project can be cloned at GitHub at RobotWalker

I will probably be refining this sometime in the future. One good idea is to create a delay between the swings of different legs. Any thoughts suggestions on making the movement more fluid are more than welcome.

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