The Coupled Drives rig shown below is a laboratory scale plant representing a material handling system, where control of speed and tension is required. Examples of similar real world systems include, amongst others, strip metal and wire manufacturing, the paper making industry and the manufacture of textile fibres.
A schematic of the rig is shown below, along with a description of the inputs and outputs. The rig may be set up as either a Single or a Multivariable problem. In the Multivariable case the degree of dynamical coupling between the tension and the speed of the rig is high and the primary control objective is to decouple these two outputs; i.e. it is desired that the drive motors (motors 1 & 2) should be driven in such a way that independent control of both speed and tension is possible.
The control of the system involves four steps: identification and estimation of discrete-time reduced order, linear models of the system using advanced identification and estimation techniques developed in CRES; the use of these models for design of a PIP true digital controller; initial evaluation of the design using computer simulation (in Matlab/Simulink); and finally, the implementation and evaluation of the controller on the real system.
Having undertaken the first three steps, the PIP controller is implemented on the Coupled Drives Rig using a 486-PC with the control algorithm written in Quick Basic. The PIP control law is implemented in a special incremental form which form allows for simple constraints to be placed on the inputs removing the problem of 'integral wind-up'. The open loop system is compared with the system under closed loop PIP control in the results below. These demonstrate how the two channels are almost completely decoupled by the controller.
The Coupled Drives Rig used in this project was lent to CRES from Sunderland University by Prof. C. Cox.
For more information you could consult the publication relevant to this topic listed on my main project page (or after September my thesis)
Roger's home page, pile driver project , inverted pendulum project
