Heavy Duty Lift

lift

Starting the Lift

The sensors node is one of the most important node as it controls the communication with three control boards.

rosrun mbs_rp_lift sensors

The node offers the following functionalities for the corresponding boards:

  1. Arm power control: board offers rosservice set_arm_power, a call to this service would switch on/off the Panda arm. Please keep in mind if the arm is switched on and the node is turned down, this will switch off the arm as well.

  2. Soft switches control: board publishes the status of soft switches on topic soft_switches_status. The topic is subscribed by the driver node and the status is used for the lift control.

  3. Lift encoder: The external rope encoders status is published on lift_joint_states topic.

For convenience to launch both lift_utils and driver node, the following launch file can be run:

roslaunch mbs_rp_lift rp_lift.launch

Attention

In case of some failure and the soft switches are bypassed. Hard switches will cut the power connection to the lift. The normal driver will stop working when hard switches are in failure state. So to bypass all safety checks of driver node, manual control node needs to be used.

Hard Switch Override

The manual_control ros node is used to override the hardswitches. With this node brakes needs to be release and applied manually. Additionally, it sends the movements command accordingly. Depending upon which switches are pressed all the information on how to get out of failure state is printed in the console.

To release the brakes:

rosservice call /apply_brake 'data: False'

To apply the brakes:

rosservice call /apply_brake 'data: True'

Lift Velocity

The driver node is the main control node to move the lift:

rosrun rp_lift driver

It offers a ROS service to move the lift up and down.

To move the lift up:

rosservice call /set_lift_velocity 'data: 2047'

To move the lift down:

rosservice call /set_lift_velocity 'data: -2047'

Positive values are to move the lift upwards and negative to move downwards. The driver take a value between -2047 and 2047.

Important

These values are micro-steps not meters per second as offered by the motor driver for the lift. The driver checks the status of soft and hard switches all the time and provides corresponding control and advice for each state.