Pneumatic PID with Ultrasonic Distance Feedback

Abstract

Indiana University–Purdue University Indianapolis (IUPUI) is initiating a new course to the Electrical & Computer Engineering Technology (ECET) Curriculum in the spring of 2019, this course is Advanced Process Controls. The lab curriculum for this course needed a functional application to demonstrate the use of a proportional–integral–derivative controller (PID). The lab location for this course has one important limitation, specifically no use of water; therefore, our design integrates the use of pneumatics. Using the lab’s existing Rockwell Automation PLC and software package, this design uses the PLC’s PID instruction to maintain an extension length on a pneumatic single acting cylinder. This closed control loop consists of the PLC and analog I/O card, an ultrasonic distance sensor, one pneumatic cylinder for the controlled variable, one pneumatic cylinder as a disturbance, and two Proportion-Air QB1X analog controlled pneumatic solenoids. The final design in summary, uses the ultrasonic sensor to provide feedback to the PID with the current extended length of the pneumatic cylinder. This establishes any error, and the properly tuned PID uses this feedback to respond accordingly to ensure the desired extension length of the cylinder is maintained.