Modelling Compression Spring

[nyxaria]

Hello, I am currently trying to set up a Series Elastic Actuator, which can exert a small force (~20N) in both directions, and has a compression spring with stiffness of k=2144.3N/m

I have set up a prismatic joint in my URDF, but am unsure how to configure it now in PyBullet.

This is what I have:

controller = Controller()

    cli = p.connect(p.GUI)  # or p.DIRECT for non-graphical version

    p.setAdditionalSearchPath(pybullet_data.getDataPath())
    p.setGravity(0, 0, -9.812)
    plane = p.loadURDF("plane.urdf")

    robot_start_pos = [0, 0, 1]
    robot_start_orientation = p.getQuaternionFromEuler([0, 0, 0])
    robot = p.loadURDF("robot.urdf", robot_start_pos, robot_start_orientation, flags=p.URDF_USE_INERTIA_FROM_FILE)

    steps_per_second = 70
    print("Total number of joints:", p.getNumJoints(robot))
    controllable_joints = []
    for index in range(p.getNumJoints(robot)):
        info = p.getJointInfo(robot, index)
        if info[2] != p.JOINT_FIXED:  # we are looking for joints we can control
            joint = Joint(info[0], info[1], info[2], info[6], info[7], info[8], info[9], info[10], info[11])
            controllable_joints.append(joint)
        if info[2] == p.JOINT_PRISMATIC:
            set_joint_to_series_elastic_actuator()
    print("Controllable Joints:")
    pp.pprint(controllable_joints)
     
# step code omited

How would I go about implementing set_joint_to_series_elastic_actuator()?