WheeledWalkMC.h

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//-*-c++-*-
#ifndef INCLUDED_WheeledWalkMC_h_
#define INCLUDED_WheeledWalkMC_h_

#include "Motion/MotionCommand.h"
#include "Motion/MotionManager.h"
#include "Shared/get_time.h"
#include "Shared/RobotInfo.h"
#include "Shared/plist.h"

//! Provides a 'WalkMC' implementation for wheeled robots (diff-drive or theoretically holonomic configurations as well)
/*! Uses kinematic description to determine location and orientation of wheels
 *  and computes appropriate wheel velocities to produce a target motion.
 *  Can handle skid-steer (diff drive) type motion, including holonomic wheels,
 *  but does not handle ackerman style (steered) configurations.
 *  
 *  Also does not handle 'slanted' wheels optimally: Assumes wheels are perpendicular
 *  to the ground, that the base frame Z axis is perpendicular to the ground frame.
 *  This could be added with a bit more math when computing wheel positions.
 *
 *  This motion command also assumes that wheels are commanded by mm/sec ground
 *  speed, not rad/sec rotational speed.
 *
 *  For simulation in Mirage, make sure all wheels are marked by adding a Velocity=true
 *  entry in the ControllerInfo of the corresponding kinematics configuration, and that
 *  the x and y dimensions of the collision model are set for the wheel radius.
 *
 *  TODO: Test on a holonomic platform, should handle it, but originally only
 *  tested on diff-drive like Create.  Also, perhaps add config settings to override #center and
 *  a flag to have updateWheelInfo called before each updateOutputs. */
class WheeledWalkMC : public MotionCommand, public virtual plist::Dictionary {
public:
  //! constructor
  WheeledWalkMC() : plist::Dictionary(), MotionCommand(),
    preferredXVel(), preferredYVel(), preferredAngVel(), 
    targetVel(), targetAngVel(0), maxVel(), maxAngVel(0),
    center(), displacementMode(false), travelTime(0), travelDur(0), dirty(false)
  {
    addEntry("PreferredXVel",preferredXVel,"optimal X velocity for unspecified displacements (mm/s)");
    addEntry("PreferredYVel",preferredYVel,"optimal Y velocity for unspecified displacements (mm/s)");
    addEntry("PreferredAngVel",preferredAngVel,"optimal angular velocity for unspecified displacements (rad/s)");
    setLoadSavePolicy(FIXED,SYNC);
    resetConfig();
  }
  
  void resetConfig(); //!< reset and reload configuration settings, implies call to updateWheelInfo()

  virtual int updateOutputs();
  virtual int isDirty() { return dirty; }
  virtual int isAlive() { return !displacementMode || getTravelTime()>=travelDur || dirty; }
  virtual void start();
  virtual void stop();
  
  //! Posts a LocomotionEvent and sets velocities to zero. Also forces an output frame setting wheel velocities to zero; needed because if we remove a motion command there may be nothing left to zero the velocities.
  virtual void zeroVelocities();
  
  float getMaxXVel() const { return maxVel[0]; }
  float getMaxYVel() const { return maxVel[1]; }
  float getMaxAVel() const { return maxAngVel; }
  
  unsigned int getTravelTime() { return get_time()-travelTime; } //!< the amount of time (ms) we have been travelling the current vector
  
  //! Returns the current x and y velocities in mm/sec
  const fmat::Column<2>& getTargetVelocity() const { return targetVel; };
  
  //! Returns the current angular velocity in radians/sec
  float getTargetAngVelocity() const { return targetAngVel; }
  
  //! Specify the desired body velocity in x and y (millimeters per second) and angular velocity (radians per second)
  virtual void getTargetVelocity(float &xvel, float &yvel, float &avel) {
    xvel = targetVel[0];
    yvel = targetVel[1];
    avel = targetAngVel;
  }
  
  //! Specify the desired body velocity in x and y (millimeters per second) and angular velocity (radians per second); does not stop automatically
  virtual void setTargetVelocity(float xvel, float yvel, float avel);
  
  //! Specify the desired body velocity in x and y (millimeters per second) and angular velocity (radians per second), and amount of time before stopping
  virtual void setTargetVelocity(float xvel, float yvel, float avel, float time);
  
  //! Specify the desired body displacement in x and y (millimeters) and a (radians)
  /*! Corresponding velocity will be limited to max velocity, so setting time=0 implies max speed */
  virtual void setTargetDisplacement(float xdisp, float ydisp, float adisp, float time=0);
  
  //! Recomputes wheel positions and orientations.  Automatically called by constructor, but may need to recall if wheel positions are actuated.
  /*! Includes a call to updateWheelVels() in case wheel positions change. */
  virtual void updateWheelInfo();
  
  plist::Primitive<float> preferredXVel; //!< optimal X velocity for unspecified displacements
  plist::Primitive<float> preferredYVel; //!< optimal Y velocity for unspecified displacements
  plist::Primitive<float> preferredAngVel; //!< optimal angular velocity for unspecified displacements
  
protected:
  void updateWheelVels(); //!< updates WheelInfo::targetVel values based on #targetVel and #targetAngVel
  
  fmat::Column<2> targetVel; //!< the requested xy velocity of the body (ignoring parameterized body motion, like sway or surge), millimeters per second
  float targetAngVel; //!< the requested angular velocity of the body, radians per second
  fmat::Column<2> maxVel; //!< maximum velocity in x,y
  float maxAngVel; //!< maximum angular velocity
  
  fmat::Column<2> center; //!< point to use as center of rotations, defaults to center of wheels
  bool displacementMode; //!< If true, velocity will be set to 0 when clock reaches #arrivalTime
  unsigned int travelTime; //!< the time of the last call to setTargetVelocity - handy to check the time we've been traveling current vector
  unsigned int travelDur; //!< duration in msecs for the current displacement
  bool dirty; //!< set to true by updateWheelVels(), cleared up updateOutputs()
  
  //! stores information about the configuration and current target state of each wheel
  struct WheelInfo {
    WheelInfo() : valid(false), position(), direction(), targetVel(0) {}
    bool valid; //!< set to false if the wheel axle is vertical
    fmat::Column<2> position; //!< the center of the wheel's contact
    fmat::Column<2> direction; //!< the direction of forward motion produced by this wheel
    float targetVel; //!< the current wheel velocity to supply to motman via updateOutputs, is calculated by setTargetVelocity()
  };
  WheelInfo wheels[NumWheels];
};

/*! @file
 * @brief Defines WheeledWalkMC, which provides a 'WalkMC' implementation for wheeled robots (diff-drive or theoretically holonomic configurations as well)
 * @author Ethan Tira-Thompson (ejt) (Creator)
 */

#endif