torsin_spring_demo.py

    import pybullet as p
    #This is essential, as this disables the default motor imposed by bullet. These default motors prevent overspeeding, and functions as
    #friction drives.
    p.setJointMotorControl2(self.model_unique_id, self.secondary_joint_id,
                              controlMode=p.VELOCITY_CONTROL, force=0)
    spring_angle = self.get_joint_angle()
    torque = spring_angle * self.torque_k

    #apply external force
    self.apply_external_force(force= torque * self.scaled_force_axis_c, link_index=self.child_link_id, position=self.force_pos_c)
    self.apply_external_force(force= torque * self.scaled_force_axis_p, link_index=self.parent_link_id, position=self.force_pos_p)
    # print("torque: ", torque)