differential_transmission.h

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// Copyright (C) 2013, PAL Robotics S.L.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//   * Redistributions of source code must retain the above copyright notice,
//     this list of conditions and the following disclaimer.
//   * Redistributions in binary form must reproduce the above copyright
//     notice, this list of conditions and the following disclaimer in the
//     documentation and/or other materials provided with the distribution.
//   * Neither the name of PAL Robotics S.L. nor the names of its
//     contributors may be used to endorse or promote products derived from
//     this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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// POSSIBILITY OF SUCH DAMAGE.
 
 
#pragma once
 
 
#include <cassert>
#include <string>
#include <vector>
 
#include <transmission_interface/transmission.h>
#include <transmission_interface/transmission_interface_exception.h>
 
namespace transmission_interface
{
 
class DifferentialTransmission : public Transmission
{
public:
  DifferentialTransmission(const std::vector<double>& actuator_reduction,
                           const std::vector<double>& joint_reduction,
                           const std::vector<double>& joint_offset);
 
  DifferentialTransmission(const std::vector<double>& actuator_reduction,
                           const std::vector<double>& joint_reduction,
                           bool ignore_transmission_for_absolute_encoders = false,
                           const std::vector<double>& joint_offset = std::vector<double>(2, 0.0));
 
  void actuatorToJointEffort(const ActuatorData& act_data,
                                   JointData&    jnt_data) override;
 
  void actuatorToJointVelocity(const ActuatorData& act_data,
                                     JointData&    jnt_data) override;
 
  void actuatorToJointPosition(const ActuatorData& act_data,
                                     JointData&    jnt_data) override;
 
  void actuatorToJointAbsolutePosition(const ActuatorData& act_data,
                                             JointData&    jnt_data) override;
 
  void actuatorToJointTorqueSensor(const ActuatorData& act_data,
                                         JointData&    jnt_data) override;
 
  void jointToActuatorEffort(const JointData&    jnt_data,
                                   ActuatorData& act_data) override;
 
  void jointToActuatorVelocity(const JointData&    jnt_data,
                                     ActuatorData& act_data) override;
 
  void jointToActuatorPosition(const JointData&    jnt_data,
                                     ActuatorData& act_data) override;
 
  std::size_t numActuators() const override {return 2;}
  std::size_t numJoints()    const override {return 2;}
  bool hasActuatorToJointAbsolutePosition()  const override {return true;}
  bool hasActuatorToJointTorqueSensor()      const override {return true;}
 
  const std::vector<double>& getActuatorReduction() const {return act_reduction_;}
  const std::vector<double>& getJointReduction()    const {return jnt_reduction_;}
  const std::vector<double>& getJointOffset()       const {return jnt_offset_;}
 
protected:
  std::vector<double>  act_reduction_;
  std::vector<double>  jnt_reduction_;
  std::vector<double>  jnt_offset_;
  bool ignore_transmission_for_absolute_encoders_;
};
 
inline DifferentialTransmission::DifferentialTransmission(const std::vector<double>& actuator_reduction,
                                                          const std::vector<double>& joint_reduction,
                                                          const std::vector<double>& joint_offset)
  : DifferentialTransmission(actuator_reduction, joint_reduction, false, joint_offset)
{}
 
inline DifferentialTransmission::DifferentialTransmission(const std::vector<double>& actuator_reduction,
                                                          const std::vector<double>& joint_reduction,
                                                          const bool ignore_transmission_for_absolute_encoders,
                                                          const std::vector<double>& joint_offset)
  : act_reduction_(actuator_reduction),
    jnt_reduction_(joint_reduction),
    jnt_offset_(joint_offset),
    ignore_transmission_for_absolute_encoders_(ignore_transmission_for_absolute_encoders)
{
  if (numActuators() != act_reduction_.size() ||
      numJoints()    != jnt_reduction_.size() ||
      numJoints()    != jnt_offset_.size())
  {
    throw TransmissionInterfaceException("Reduction and offset vectors of a differential transmission must have size 2.");
  }
 
  if (0.0 == act_reduction_[0] ||
      0.0 == act_reduction_[1] ||
      0.0 == jnt_reduction_[0] ||
      0.0 == jnt_reduction_[1])
  {
    throw TransmissionInterfaceException("Transmission reduction ratios cannot be zero.");
  }
}
 
inline void DifferentialTransmission::actuatorToJointEffort(const ActuatorData& act_data,
                                                                  JointData&    jnt_data)
{
  assert(numActuators() == act_data.effort.size() && numJoints() == jnt_data.effort.size());
  assert(act_data.effort[0] && act_data.effort[1] && jnt_data.effort[0] && jnt_data.effort[1]);
 
  const std::vector<double>& ar = act_reduction_;
  const std::vector<double>& jr = jnt_reduction_;
 
  *jnt_data.effort[0] = jr[0] * (*act_data.effort[0] * ar[0] + *act_data.effort[1] * ar[1]);
  *jnt_data.effort[1] = jr[1] * (*act_data.effort[0] * ar[0] - *act_data.effort[1] * ar[1]);
}
 
inline void DifferentialTransmission::actuatorToJointVelocity(const ActuatorData& act_data,
                                                                    JointData&    jnt_data)
{
  assert(numActuators() == act_data.velocity.size() && numJoints() == jnt_data.velocity.size());
  assert(act_data.velocity[0] && act_data.velocity[1] && jnt_data.velocity[0] && jnt_data.velocity[1]);
 
  const std::vector<double>& ar = act_reduction_;
  const std::vector<double>& jr = jnt_reduction_;
 
  *jnt_data.velocity[0] = (*act_data.velocity[0] / ar[0] + *act_data.velocity[1] / ar[1]) / (2.0 * jr[0]);
  *jnt_data.velocity[1] = (*act_data.velocity[0] / ar[0] - *act_data.velocity[1] / ar[1]) / (2.0 * jr[1]);
}
 
inline void DifferentialTransmission::actuatorToJointPosition(const ActuatorData& act_data,
                                                                    JointData&    jnt_data)
{
  assert(numActuators() == act_data.position.size() && numJoints() == jnt_data.position.size());
  assert(act_data.position[0] && act_data.position[1] && jnt_data.position[0] && jnt_data.position[1]);
 
  const std::vector<double>& ar = act_reduction_;
  const std::vector<double>& jr = jnt_reduction_;
 
  *jnt_data.position[0] = (*act_data.position[0] / ar[0] + *act_data.position[1] / ar[1]) / (2.0 * jr[0]) + jnt_offset_[0];
  *jnt_data.position[1] = (*act_data.position[0] / ar[0] - *act_data.position[1] / ar[1]) / (2.0 * jr[1]) + jnt_offset_[1];
}
 
inline void DifferentialTransmission::actuatorToJointAbsolutePosition(const ActuatorData& act_data,
                                                                            JointData&    jnt_data)
{
  assert(numActuators() == act_data.absolute_position.size() && numJoints() == jnt_data.absolute_position.size());
  assert(act_data.position[0] && act_data.absolute_position[1] && jnt_data.absolute_position[0] && jnt_data.absolute_position[1]);
 
  const std::vector<double>& ar = act_reduction_;
  const std::vector<double>& jr = jnt_reduction_;
 
  if(!ignore_transmission_for_absolute_encoders_)
  {
    *jnt_data.absolute_position[0] = (*act_data.absolute_position[0] / ar[0] + *act_data.absolute_position[1] / ar[1]) / (2.0 * jr[0]) + jnt_offset_[0];
    *jnt_data.absolute_position[1] = (*act_data.absolute_position[0] / ar[0] - *act_data.absolute_position[1] / ar[1]) / (2.0 * jr[1]) + jnt_offset_[1];
  }
  else
  {
    *jnt_data.absolute_position[0] = *act_data.absolute_position[1];
    *jnt_data.absolute_position[1] = *act_data.absolute_position[0];
  }
}
 
inline void DifferentialTransmission::actuatorToJointTorqueSensor(const ActuatorData& act_data,
                                                                        JointData&    jnt_data)
{
  assert(numActuators() == act_data.torque_sensor.size() && numJoints() == jnt_data.torque_sensor.size());
  assert(act_data.torque_sensor[0] && act_data.torque_sensor[1] && jnt_data.torque_sensor[0] && jnt_data.torque_sensor[1]);
 
  const std::vector<double>& ar = act_reduction_;
  const std::vector<double>& jr = jnt_reduction_;
 
  *jnt_data.torque_sensor[0] = jr[0] * (*act_data.torque_sensor[0] * ar[0] + *act_data.torque_sensor[1] * ar[1]);
  *jnt_data.torque_sensor[1] = jr[1] * (*act_data.torque_sensor[0] * ar[0] - *act_data.torque_sensor[1] * ar[1]);
}
 
inline void DifferentialTransmission::jointToActuatorEffort(const JointData&    jnt_data,
                                                                  ActuatorData& act_data)
{
  assert(numActuators() == act_data.effort.size() && numJoints() == jnt_data.effort.size());
  assert(act_data.effort[0] && act_data.effort[1] && jnt_data.effort[0] && jnt_data.effort[1]);
 
  const std::vector<double>& ar = act_reduction_;
  const std::vector<double>& jr = jnt_reduction_;
 
  *act_data.effort[0] = (*jnt_data.effort[0] / jr[0] + *jnt_data.effort[1] / jr[1]) / (2.0 * ar[0]);
  *act_data.effort[1] = (*jnt_data.effort[0] / jr[0] - *jnt_data.effort[1] / jr[1]) / (2.0 * ar[1]);
}
 
inline void DifferentialTransmission::jointToActuatorVelocity(const JointData&    jnt_data,
                                                                    ActuatorData& act_data)
{
  assert(numActuators() == act_data.velocity.size() && numJoints() == jnt_data.velocity.size());
  assert(act_data.velocity[0] && act_data.velocity[1] && jnt_data.velocity[0] && jnt_data.velocity[1]);
 
  const std::vector<double>& ar = act_reduction_;
  const std::vector<double>& jr = jnt_reduction_;
 
  *act_data.velocity[0] = (*jnt_data.velocity[0] * jr[0] + *jnt_data.velocity[1] * jr[1]) * ar[0];
  *act_data.velocity[1] = (*jnt_data.velocity[0] * jr[0] - *jnt_data.velocity[1] * jr[1]) * ar[1];
}
 
inline void DifferentialTransmission::jointToActuatorPosition(const JointData&    jnt_data,
                                                                    ActuatorData& act_data)
{
  assert(numActuators() == act_data.position.size() && numJoints() == jnt_data.position.size());
  assert(act_data.position[0] && act_data.position[1] && jnt_data.position[0] && jnt_data.position[1]);
 
  const std::vector<double>& ar = act_reduction_;
  const std::vector<double>& jr = jnt_reduction_;
 
  double jnt_pos_off[2] = {*jnt_data.position[0] - jnt_offset_[0], *jnt_data.position[1] - jnt_offset_[1]};
 
  *act_data.position[0] = (jnt_pos_off[0] * jr[0] + jnt_pos_off[1] * jr[1]) * ar[0];
  *act_data.position[1] = (jnt_pos_off[0] * jr[0] - jnt_pos_off[1] * jr[1]) * ar[1];
}
 
} // transmission_interface