GM: use torque controller

[sshane]

Most GMs are dashcammed, so this only affects Volt, Acadia, Escalade

[hewers]

Could delete old feedforward functions with this change? Thanks!

  # Determined by iteratively plotting and minimizing error for f(angle, speed) = steer.
  @staticmethod
  def get_steer_feedforward_volt(desired_angle, v_ego):
    desired_angle *= 0.02904609
    sigmoid = desired_angle / (1 + fabs(desired_angle))
    return 0.10006696 * sigmoid * (v_ego + 3.12485927)
  @staticmethod
  def get_steer_feedforward_acadia(desired_angle, v_ego):
    desired_angle *= 0.09760208
    sigmoid = desired_angle / (1 + fabs(desired_angle))
    return 0.04689655 * sigmoid * (v_ego + 10.028217)
  def get_steer_feedforward_function(self):
    if self.CP.carFingerprint == CAR.VOLT:
      return self.get_steer_feedforward_volt
    elif self.CP.carFingerprint == CAR.ACADIA:
      return self.get_steer_feedforward_acadia
    else:
      return CarInterfaceBase.get_steer_feedforward_default