variable_motorSpeed = 0
def start():
    global variable_motorSpeed
    robot_ctrl.set_mode(rm_define.robot_mode_free)
    while True:
        variable_motorSpeed = 20
        chassis_ctrl.set_pwm_value(rm_define.pwm1, 8)
        chassis_ctrl.set_wheel_speed(variable_motorSpeed,0,0,0)
        time.sleep(0.5)
        variable_motorSpeed = 40
        chassis_ctrl.set_pwm_value(rm_define.pwm1, 9)
        chassis_ctrl.set_wheel_speed(variable_motorSpeed,0,0,0)
        time.sleep(0.5)
        variable_motorSpeed = 0
        chassis_ctrl.set_pwm_value(rm_define.pwm1, 7.5)
        chassis_ctrl.set_w