Controller for a spider-cam-like positioner (cable suspended robot).
This project provides a system to control a cable suspended robot with arbitrary number of cables. It cares about the calculation of the cable lengths and rotation speeds for each winch when moving the platform to a new target position. It is assumed that the axes are interfaced using the StepperDrive motor controller boards.
Clone this repository somewhere to the host computer that will control your devices.
In the newly created directory, install the package with: pip install .
Now, you can import spiderrobot from anywhere on that computer in python.
- Define a coordinate system in the real world for the application, i.e. where the target is moving in and the motor axes are placed.
- Instantiate the Positioner class with the serial interface for the motor controller and the initial target position.
- Add motor abstractions using the "addAxis" method with the motor id, position of the axis and the axle diameter in meters.
- Move the target using the "moveToPos([x, y, z], velocity)" method, with argumements being metric.
Note:
The system is only constrained on a point, but not while moving between two points!
When the next target position is far away from the last position, use moveOnLine instead of moveToPos.
The robot will then split the line into intermediate points between the last and target position in sections of 0.1 m by default.
Otherwise, the cables are likely to derail.
from spiderrobot import Positioner
# start position
pos = [0., 0., 0.13]
# initialize positioner with initial target position
p = Positioner('/dev/tty.usbserial-A50285BI', pos)
# add axes with their positions
nomX = 2.5-0.048 # nominal x length from origin
nomY = 1.25+0.013 # nominal y length from origin
nomZ = 2.5-0.1 # nominal z length from origin
p.addAxis(1, [nomX, nomY, nomZ])
p.addAxis(2, [-nomX, nomY, nomZ])
p.addAxis(3, [-nomX, -nomY, nomZ])
p.addAxis(4, [nomX, -nomY, nomZ])
# move platform to 1.24 m up with 0.05 m/s
p.moveToPos([0., 0., 1.24], 0.05)