Actuator model for robots

[geraldb]

1. k_p should be in actuator coordinates
2. when trajectory is in non-task coordinates: system fails
3. actuator should be modeled in the simulation dynamics, not in the controller

[Samir Menon]

Added an API for an actuator model : 86effa18af30ff1f7cfc1825275c7a609591549b

Now have to reorganize the dynamics to use it, if required.

[Samir Menon]

Issue #27 was marked as a duplicate of this issue.

[Samir Menon]

Robert's requirements:

the current implementation does not allow to specify the minimum and maximum torque for each joint. A decent approach would be to allow the following specification:

Model: torqueMin = minimumTorque + qd * torqueChangeLinear + qd^2 * torqueChangequadratic torqueMax = maximumTorque + qd * torqueChangeLinear + qd^2 * torqueChangequadratic

Addition to the Spec File for each link: <minimumTorque> -70.0 </minimumTorque> <!--Unit: Nm--> <maximumTorque> 70.0 </maximumTorque> <!--Unit: Nm--> <torqueChangeLinear> 3.0 </torqueChangeLinear> <!--Unit: Ns--> <torqueChangeQuadratic> 2.0 </torqueChangeQuadratic> <!--Unit: Ns^2-->

[Robert Katzschmann]

torque limits can be found in SRobotParsedData:

  /** The actuators' max force limits */
  Eigen::VectorXd max_actuator_forces_;

  /** The actuators' min force limits */
  Eigen::VectorXd min_actuator_forces_;

what do I need to write in the specs file to write to this variable?

[Samir Menon]

Reducing priority. There seems to be no immediate need apart from Muscles, which are under heavy development anyway. Moreover, muscles are a big enough issue to warrant separate attention.