[ODE] a newbie in ODE

Jacky - jacky_coolheart at yahoo.com
Fri May 4 01:59:13 MST 2007

  I'm a newbie in ODE and I got a project using ODE. I am a computer science student
  so my physics is not really good. There are several stuff that I want to ask.
  Problem description:
  I'm trying to build a bipedal walking. All of the joints are connected by hinge joints.
  All of the parameters setting (CFM, ERP, and others) I leave it to the default value. 
  The world step is 0.01. The biped model is only two legs, the body is a block, no hands, no head.
  The model is just blocks connected by hinge joints.
  1. Regarding servo motors. Is there any need to use Amotor for the hinge joints?
  Currently I'm using the following: 
  dReal Gain = 0.1;
  dReal MaxForce = 100;
  dReal TruePosition = dJointGetHingeAngle(joint_kneeLeft);
  dReal DesiredPosition = <<angleTarget>>;
  dReal Error = TruePosition - DesiredPosition;
  dReal DesiredVelocity = -Error * Gain;
  dJointSetHingeParam(joint_kneeLeft, dParamFMax, MaxForce);
  dJointSetHingeParam(joint_kneeLeft, dParamVel, DesiredVelocity);
  Is the above code equivalent as a servo motor simulation? Or I should use Amotor instead?
  2. For the leg, block is stacking each other (the thigh block is stacking on top of the shin block).
  It means in the simulation, collision detection is done between these two blocks. I know that for some
  cases, they will jitter and shaking. I also had the same problem, but after I tweak the parameters in the 
  nearCallback function, it is fine. 
  Should I let the blocks keep penetrating each other by allowing collition detection performed on them?
  Or I should disable the collision detection and place joint limit instead?
  3. Example code.
  Anybody could give me an example code simulating a biped walking? That will be a great help and will answer all the above questions 
  4. Another problem.
  If I want to simulate a leg jumping (just a single leg let's say) , how could I simulate it? 
  I don't understand the physics concept needed, like the inertia, momentum, how much force
  required and so on. 
  Should I model something like spring/damper or whatever?
  spring/damper --> (I just read from the ODE manual and I don't know how to simulate it)
  Thanks in advance for anybody post an reply answer to my questions/problems. Thx.

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