Stewart Platforms
Table of Contents
The goal of this project is to provide a Matlab/Simscape Toolbox to study Stewart platforms. The project is divided into several section listed below. The git repository of the project is accessible here.
1 Simulink Project (link)
The project is managed with a Simulink Project. Such project is briefly presented here.
2 Stewart Platform Architecture Definition (link)
The way the Stewart Platform is defined is explained here.
All the geometrical parameters are defined including:
- Definition of the location of the frames
- Location/orientation of the limbs
- Size/inertia of the platforms and the limbs
Other parameters are also defined such as:
- Stiffness and damping of the struts
- Rest position of the Stewart platform
3 Simscape Model of the Stewart Platform (link)
4 Kinematic Analysis (link)
From the defined geometry of the Stewart platform, we can perform static analysis such as:
- Jacobian Analysis that links the velocity of each limb to the velocity of the mobile platform
- Static Forces Analysis that links the forces applied by each limb to the resulting force/torque applied to the mobile platform
From the strut stiffness, we can also perform a Stiffness Analysis that consists of determining the Stiffness matrix and Compliance matrix of the Stewart platform from the geometry.
All these analysis are described here.
5 Identification of the Stewart Dynamics (link)
The Dynamics of the Stewart platform can be identified using the Simscape model.
It is possible to:
- Determine the dynamics from the actuators to the various sensors included in the Stewart platform
- Extract State Space models for further analysis / control synthesis
- Extract the Resonant Frequencies, Modal Damping, and associated Mode Shapes
The code that is used for identification is explained here.
6 Control
The use of active control for Stewart platforms is a wide subject. Many aspect can be studied.
The sensors used is of primary important. We can have:
- Sensors located in each strut: relative motion, force sensor, inertial sensor
- Sensors measuring the relative motion between the fixed base and the mobile platform
- Inertial sensors located on the mobile platform
The control objective can also vary:
- Reference Tracking
- Active Damping
- Vibration Isolation
The Control for Stewart platforms is here studied in the following files:
- Active Damping (link).
The use of different sensors are compared for active damping:
- Inertial Sensor in each strut or fixed to the mobile platform
- Force Sensor in each strut
- Relative Motion Sensor in each strut
- Motion Control (link). Different control architectures (centralized and decentralized) are compared for the position control of the Stewart platform.
- Vibration Isolation (link)