Python Motion Platform Controller

This software enables a motion simulator or other client to control movement of version 2 of the Middlesex University motion platform.

Platform Hardware Overview

The motion platform is an inverted Stewart platform. It has a fixed base and a moving platform connected with six pneumatic actuators. Adjusting the lengths of the actuators moves the platform in six degrees of freedom (front/back, left/right, up/down, roll, pitch and yaw). The pneumatic actuator lengths are controlled using Festo precision industrial pressure valves.

Software Overview

All activity is driven from the controller module through service calls that poll the client every 50 milliseconds. The client responds with orientation requests and/ or system commands. Orientation requests are in the form surge, sway, heave, roll, pitch, and yaw. These can be either real world values (mm and radians) or normalized values (values between -1 and 1 representing the maximum range of movement of the platform for each degree of freedom).

Note that the system needs most of the 50ms interval between service requests to calculate and drive the output; therefore the client must return promptly from the service calls. If necessary, the client can use the threaded client example as a model to decouple client processing from the system service routine.

Installation

Install the software by copying all the files including the two subdirectories (client and fstlib) directories to your PC. The software can run in any directory and no registry entries are needed. Install Python 2.7 if not already installed. The following python modules are required to run with the example clients: sys, time, math, copy, numpy, collections, traceback, socket, TKinter, tkMessageBox, ttk, pillow The threaded client example also requires: Queue, threading

Note the roller coaster client code in coaster directory will not be publically distributed. This software requires a licensed version of NoLimits2 and the following python modules: serial, win32gui, win32api, win32con, ctypes

The software consists of the following elements:

(see comments in source code for more details)

Client examples:

• platform_input.py - keyboard input of orientation values
• platform_input_tk.py - tkinter gui input of orientation values, also include graphical display of output
• platform_input_UDP.py - orientation values sent as USP messages
• platform_input_threadedUDP.py – as above but UDP socket is on separate thread

Controller

• platform_controller.py - the main system module
• shape.py - controls gain, washout and smoothing
• shape.cfg - stores saved settings
• kinematics.py - calculates platform actuator lengths from orientation requests
• moving_average.py - smooths data

Output

• platform_output.py - converts actuator requests to festo commands
• output_gui.py – optional tkinter display of output state

Platform Config files: - these contain information on the physical properties of the platform

• ConfigV1.py – config for original motion platform
• ConfigV2.py - config for the second generation platform

Images

Contains the icons and images used in the TK GUI

Fstlib

Contains the festo driver software

Coaster Client code (not for public distribution):

• coaster_client.py
• coaster_gui.py
• coaster_interface.py
• quaternion.py
• serial_remote.py
• MoveState.py