Kinematic Trajectory and Force Capture System
Advait Jain (http://www.cc.gatech.edu/~advait)
What this does
This page describes the capture system that we designed to log the kinematic trajectory through which mechanisms (doors and drawers) move and the forces used to operate them.
We first used this setup in this paper: The Complex Structure of Simple Devices: A Survey of Trajectories and Forces that Open Doors and Drawers. Advait Jain, Hai Nguyen, Mrinal Rath, Jason Okerman, and Charles C. Kemp. IEEE RAS/EMBS International Conference on Biomedical Robotics and Biomechatronics (BIOROB), 2010. This paper and others can be downloaded from the Heathcare Robotics Lab website (http://www.healthcare-robotics.com)
Pictures of the Setup
This is the hardware setup that we use:
- Tilting servo: Robotis Servo (typically we use RX-28) http://www.crustcrawler.com/motors/RX28/index.php?prod=66
- This gives a serial interface to control the servo: http://www.crustcrawler.com/electronics/USB2Dynamixel/index.php?prod=65
- Hokuyo UTM. (http://www.acroname.com/robotics/parts/R314-HOKUYO-LASER4.html)
- Bracket to mount the Hokuyo on to the servo.
- This is a custom part that we have designed.
- The solidworks CAD file (utm-servo-bracket.sldprt). This requires Solidworks 2009.
- We have taken two routes for making the bracket
- We thank Abhishek Bhatkhande for making the CAD model from the bracket design.
- Four M2x4 (2mm diameter, 4mm length) to connect the servo to the bracket.
- Two M3x6 or M3x8 to connect the UTM to the bracket.
- Longer screws will require washers.
The image on the right shows how we power the Robotis servos and connect to the USB2Dynamixel converter.
- The block labeled 12V is a power supply that takes unregulated 24V as input (red and white cables ending in a connector) and gives 12V regulated as output. Regulated power is not required for the servos but we also use the same power supply for Hokuyos and so find it convenient. RX28 servos can take between 12V and 16V (I think. Please read the manual to confirm).
- The output of this power block in the image is are the green (GND) and red (12V) wires.
- GND goes to both the USB2Dynamixel and the Robotis servo.
- 12V goes to the servo only. Notice that a cable on the USB2Dynamixel is clipped. This is intentional and is the one that is labeled N/C on the USB2Dynamixel. Connecting 12V to that causes the USB2Dynamixel to burn.
- The rest of the wiring from the USB2Dynamixel is simply straight connections for the RS485 communication.
- The RX28's communicate using RS485 protocol. Ensure that the USB2Dynamixel toggle switch is set to RS485.
- ROS (http://www.ros.org)
- You will need the following ROS packages from our public ROS repository (available at http://code.google.com/p/gt-ros-pkg/wiki/hrl_content_summary)