RoboSavvy Forum

EZPhysics Simulator: Stable and Documentation now available

2011-05-11T10:53:26+01:00

Hi all

EZPhysics is a 3D physics simulator, part of the Actuated Character project ( http://actuated.wordpress.com/ ) that RoboSavvy has been developing.

The software has been receiving a significant overhaul and improvement and has now reached a stage where is is mature enough and documentation is available for GA.

One interesting bit is that we particularly like is that you can a full simulation or interface/control the simulation feeding external data over TCP/IP (for use with Matlab for example).

As I mentioned, the project is open source and all resources are available here http://ezphysics.org

Regards
Pedro

Statistics: Posted by PedroR — Wed May 11, 2011 10:53 am

Actuatedcharacter

2011-04-21T00:25:44+01:00

The ActuatedCharacter project is progressing steadily. There are a couple of stable firmwares for AX12 and CM5 and Linux that provide a foundation for fixed frame-rate control of the servos using direct PWM control ar PD control including speed control (not only position control).
The embedded linux can run Matlab code and do the closed loop at some 200Hz. Works with both the real robot and ezphysics.org simulated robot.

Anyone interested in a rigorous approach to understanding every aspect of the behavior of the robot and being able to control it using optimal/robust controler such as DLQR should check out recent developments at http://actuated.wordpress.com

Statistics: Posted by limor — Thu Apr 21, 2011 12:25 am

Actuatedcharacter

2010-12-15T04:51:18+01:00

Really great work, thanks for making it available!

Statistics: Posted by Fraser — Wed Dec 15, 2010 4:51 am

Actuatedcharacter

2010-12-15T01:24:10+01:00

EZPhysics (Ogre3D + ODE real-time simulator) is progressing nicely.
you can already download and compile from SVN.
a pre-packaged zip with executable and redistributables will be available soon.

Statistics: Posted by limor — Wed Dec 15, 2010 1:24 am

Actuatedcharacter

2010-09-23T17:51:52+01:00

Another piece of blog talks about the use of RoBoard connected with CM5 over FTDI.

http://actuated.wordpress.com

Statistics: Posted by limor — Thu Sep 23, 2010 5:51 pm

Actuatedcharacter

2010-09-23T17:37:53+01:00

EZPhysics.org which is a system that exposes all of ODE's features through a GUI and integrates ODE with Ogre3D (i wrote it back in 2003 as a way to learn these systems and to simulate robots in real-time) has been revamped. The code is now compatible with the latest versions of Ogre and ODE.

Progress can be seen on the blog. http://actuated.wordpress.com

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Statistics: Posted by limor — Thu Sep 23, 2010 5:37 pm

Actuatedcharacter

2010-07-25T15:36:52+01:00

I was more asking for my sake. I have a lot of experience with physics engines, but that experience is several years old now.

My plan was to go with Bullet over ODE because Erwin is still active in it where Russell has not been active in the development of ODE for years. Worst case I'll contribute to Bullet or just write my own simulator again. My project does not have a timeline, so I have the luxury of such things.

In that thread it looks like the main complaint was mass ratios. For what you're doing that should not really be a problem, but who knows. Back a few years the most precise simulator was Newton, but its development looks pretty dead now.

If ODE is currently working for you, I'd say stick with it.

Statistics: Posted by billyzelsnack — Sun Jul 25, 2010 3:36 pm

Actuatedcharacter

2010-07-25T12:39:40+01:00

billyzelsnack wrote:
So why ODE instead of Bullet?

not being familiar with Bullet, we relied on some googling and found some posts saying that for robot simulation Bullet is not as "good" as ODE. For example this thread. Can't quantify this assessment. I know what to do if I need to write my own servo simulator using sampled data with ODE. Dont know anything about Bullet.

What's your experience?

Statistics: Posted by limor — Sun Jul 25, 2010 12:39 pm

Actuatedcharacter

2010-07-24T22:35:28+01:00

So why ODE instead of Bullet?

Statistics: Posted by billyzelsnack — Sat Jul 24, 2010 10:35 pm

Actuatedcharacter

2010-07-24T20:20:21+01:00

3impact definitely looks nice, small and clean code. with impressive demos. I'm familiar with Ogre3d.org which is the heavy-weight of opensource 3D engines. but good to know about this engine.

the challenge really is (a) getting all the inertial parameters into the 3D/ODE model and (b) then to somehow model the AX12 servos control.

Since the self-balancing robot is in perpetual motion, the PWM position-holding control offered by AX12 (and any other RC servo) is useless (*).
The only useful things contrallable with AX12 is power (torque) and direction of rotation (there is no speed control). There is a very high amount of power needed to start the AX12 rotating but once it gets going, it is possible to reduce the torque.

What I suspect we will have to do is initially model the AX12 as a motor with high internal friction (starting friction and then motion friction). Eventually, we will have to sample AX12 servos and just use the sampled data in place of the motor control mathematical model.

Therefore, 3dimpact may be able to give some shortcuts in getting quick visual mapping between ODE and graphics. For now we have started with something i have written many years ago called ezphysics.org. we have updated it to the latest version of Ogre3D and ODE and it seems to be running ok.

(*) PWM holding position feature of the servos may be useful not at the actual target position but at the peripheries. since if you use a 0 punch and big CW value (tolerance around the target position), it is simulating a sort of spring effect. they may turn out to be useful.

Statistics: Posted by limor — Sat Jul 24, 2010 8:20 pm

3impact

2010-07-24T12:45:32+01:00

You might want to try the free 3impact engine (http://www.3impact.com), nice wrapper arround ODE (mesh-ball and ball-ball collisions, also implementing ragdolls) and Direct3D (including skinmesh) and nice Sound engine with Doppler effect. Had port its C API to Pascal and created OOP API layer over it in the past (for Delphi) and others followed up (see the forums there) with OOP layers for .NET etc.

Statistics: Posted by birbilis — Sat Jul 24, 2010 12:45 pm

Actuatedcharacter

2010-07-20T00:01:59+01:00

Another thread started by billyzelsnack here on the forum has preceeded this in discussing the idea of using a bridge board between the PC/USB/FTDI and the dynamixel bus in order to circumvent the limitations of USB's 1ms frame rate.

http://robosavvy.com/forum/viewtopic.php?t=5808

Statistics: Posted by limor — Tue Jul 20, 2010 12:01 am

Actuatedcharacter

2010-07-19T23:54:11+01:00

bioloidcontrol looked like a very nice project but seems to have not evolved in 2 years.

Our intention now with actuatedcharacter is to bring the physx simulator to certain level of working condition but then leave it in favor of ODE. it seems like the physx has some limitations in its ability to recreate complicated servo behavior whereas ODE is opensource and may provide an easier path to better simulation.
measuring all the physical parameters of the robots and putting them in place into the simulation is a pain. we've done it for Bioloid and there's no reason why you can't do the same for Robobuilder.

Statistics: Posted by limor — Mon Jul 19, 2010 11:54 pm

Actuatedcharacter

2010-07-18T16:45:02+01:00

Downloaded your code and got it running - looks really nice. Almost spooky as it lies there twitching!

Incidentally have you seen this site? : http://bioloidcontrol.sourceforge.net/

Statistics: Posted by l3v3rz — Sun Jul 18, 2010 4:45 pm

Actuatedcharacter

2010-07-16T19:19:33+01:00

It would be great if you build something that can act as a general simulator that can be re-configured for robobuilder as well. I've been trying to build something similar using Physx and C# (3D models in Blender) for a while. BTW The nice thing about Physx is if you have a Nvidia graphics card it can use the GPU to hardware accelerate the Physx and you get 10-100 fold speed improvement.

Heres some video of my stuff (all done in evening etc ... )

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Note in the first one its a 16 servo robot, but by the newer version I'm trying to support 18 servos as I bought the hip kit.

The problem I've hit is trying to get the model to be realistic in terms of its weight / density / physical dimensions etc etc. So if you create an open source library with say a "servo class" and some different bracket types that can then be "assembled", purely data driven that would be really cool.

Statistics: Posted by l3v3rz — Fri Jul 16, 2010 7:19 pm