Q: Is it okay to hard code length of the links for the exercises?
A: No. Your implementation should be general for ANY kinematic tree.
Q: The feet of the robot are under the ground.
A: You can change starting base height to 0.5. See GitHub issue #6.
Q: Do we need to use analytical Jacobian for IK solver?
A: No. It’s okay to use numerical Jacobian. (of couse it's okay to use analytical Jacobian too)
Q: My IK solver is very unstable. But my Jacobian is correct.
A: You may need to add regularizer to diagonal terms of Hessian or approximated Hessian.
Q: Can I increase the number of IK iteration?
A: Yes. But if you use Gauss-Newton method, 10 will be enough.
Q: (Ex.5) Do I need to generate trajectory considering the terrain height?
A: No. Adding offset (ground height) to IK target is just enough. Either way, if your robot walk on the terrain without any problem, we consider it as a successful implementation.
Q: Should I always use hint, or is it just okay to ignore it.
A: Of course it's totally fine to ignore hints we provided. But please remember, if your implementation causes some side effects (e.g. some state changes of the robot that was not expected or not intended) although your implementation seemingly do the right thing, you may lose some points. So I strongly recommend you to stick to hints and our guides as much as possible.
Q: Often the knee of the robot snap to the other way as the following image
A: We don't take into account joint limit in our IK, so it's very normal. Specifically, if a leg is in near singularity condition (due to too high forward speed command etc.) this can happen. But, if this happens too often, you should do a double check if something wrong in your implementation.
Q: Is it okay to hard code length of the links for the exercises? A: No. Your implementation should be general for ANY kinematic tree.
Q: The feet of the robot are under the ground. A: You can change starting base height to 0.5. See GitHub issue #6.
Q: Do we need to use analytical Jacobian for IK solver? A: No. It’s okay to use numerical Jacobian. (of couse it's okay to use analytical Jacobian too)
Q: My IK solver is very unstable. But my Jacobian is correct. A: You may need to add regularizer to diagonal terms of Hessian or approximated Hessian.
Q: Can I increase the number of IK iteration? A: Yes. But if you use Gauss-Newton method, 10 will be enough.
Q: (Ex.5) Do I need to generate trajectory considering the terrain height? A: No. Adding offset (ground height) to IK target is just enough. Either way, if your robot walk on the terrain without any problem, we consider it as a successful implementation.
Q: Should I always use hint, or is it just okay to ignore it. A: Of course it's totally fine to ignore hints we provided. But please remember, if your implementation causes some side effects (e.g. some state changes of the robot that was not expected or not intended) although your implementation seemingly do the right thing, you may lose some points. So I strongly recommend you to stick to hints and our guides as much as possible.
Q: Often the knee of the robot snap to the other way as the following image
A: We don't take into account joint limit in our IK, so it's very normal. Specifically, if a leg is in near singularity condition (due to too high forward speed command etc.) this can happen. But, if this happens too often, you should do a double check if something wrong in your implementation.