Brian Surgenor

A Problem With the LQ Control of Overhead Cranes

The control of an overhead crane is a classic optimum control problem, and its solution can be found in most textbooks on the subject of automatic controls. However, there is a design issue with respect to the relative mass of the cart and the suspended payload. If this problem is ignored, then the results of an analysis can be misleading and the response can be unstable. Based on a stability analysis, a design recommendation for optimal asymptotic linear quadratic (LQ) controllers with fixed gains is presented to avoid this problem. The results are validated by both simulation and experiment.

Experimental evaluation of a backlash inverter as applied to a servomotor with gear train

Tao and Kokotovic (1993) documented a method to control systems with high backlash. A right inverse of the backlash effect was derived and applied, in both a fixed and an adaptive scheme, in simulation tests of the inverters performance. The remits of the preliminary study were favourable, and these results were repeated in further simulation studies. This paper sets out to perform an experimental evaluation of the inverters effectiveness, by attempting position control of a high-backlash servomotor gear train apparatus. Tests are performed with and without the inverter, using a generic model control (GMC) scheme, to evaluate the quantitative improvement attainable by applying the inverter. This examination concluded that the inverters favourable simulation results could not be duplicated in practice. Further work is required.

The Mechatronics laboratory experience

This paper describes an approach taken to undergraduate laboratories in Mechatronics. A sequence of six laboratories culminate with an apparatus that involves the microprocessor control of a floating ping-pong ball. The apparatus consists of a cooling fan (taken from a PC) located at the base of a vertical tube (in which the ping-pong ball levitates) and an ultrasonic sensor at the top of the tube (to measure the height of the ball). The apparatus was found to be an invaluable supplement to the theory taught in the classroom, and in particular in the areas of microprocessor programming and interfacing, areas that are traditionally foreign to Mechanical Engineering students. Student experience with this apparatus relative to a much more expensive computer integrated manufacturing (CIM) assembly cell available in another course is considered. It is argued that the ping-pong ball apparatus better embodies the underlying principles of mechatronic system design, relative to the formal CIM assembly cell.

Vision Based Fault Detection of Automated Assembly Equipment

Machine faults and breakdowns are a concern for the manufacturing industry. Automated assembly machines typically employ many different types of sensors to monitor machine health and feedback faults to a central controller for review by a technician or engineer. This paper describes progress with a project whose goal is to examine the effectiveness of using machine vision to detect ‘visually cued’ faults in automated assembly equipment. Tests were conducted on a laboratory scale conveyor apparatus that assembles a simple 3-part component. The machine vision system consisted of several conventional webcams and image processing in LabVIEW. Preliminary results demonstrated that the machine vision system could identify faults such as part jams and feeder jams; however the overall effectiveness was limited as this technique can only detect faults known prior to creating the vision system. Future work to create a more robust system is currently underway.Copyright

Pulse-Width Modulation Control of a Pneumatic Positioning System

The paper describes an experimental investigation of pulse-width modulation (PWM) control of a pneumatic positioning system. PWM has been applied in the past to pneumatic positioning systems. But there are a number of different pneumatic circuit designs and PWM algorithms to choose from. This paper presents a new system design that is believed to be an improvement over previous pneumatic circuit and PWM algorithm designs. A single 3-position solenoid valve is used together with two manual flow control valves. The conventional PWM algorithm is modified with a dual switching gain to account for the valve characteristic. Test results indicate that the new system design can match the performance of previous designs. But careful consideration must be given to issues such as PWM carrier frequency and valve response times.Copyright

Control of a pneumatic gantry robot for grinding: a neuro-fuzzy approach to PID tuning

This paper addresses an application that involves the grinding of the edges of steel blanks with a pneumatic gantry robot. It presents a PID tuning method that uses an adaptive neuro-fuzzy inference system (ANFIS) to model the relationship between the controller gains and the target output response, with the response specification set by desired percent overshoot and settling time. The ANFIS based input-output model is then used to tune on-line the PID gains for different response specifications. Experimental results demonstrate that better performance can be achieved with ANFIS tuning relative to 1) Ziegler-Nichols tuning and 2) trial and error tuning. The actual response specifications with ANFIS matched the desired response specifications with an accuracy of 95%

Performance evaluation and tuning of a fuzzy control strategy for a fuel cell hybrid electric auto rickshaw

One of the most important factors that determine the performance of hybrid vehicles is the energy management and power distribution between the different energy sources. This paper reports on a project whose objective is to examine the potential and compare the performance of intelligent control strategies as applied to a fuel cell/battery hybrid electric auto rickshaw. A previous study found that a novel fuel cell load following strategy (FCLS) showed better results when compared to an equivalent consumption minimization strategy. In this paper, a fuzzy control strategy (FCS) is benchmarked against FCLS using a realistic drive cycle. It was found that after careful tuning, FCLS and FCS were equivalent in terms of achievable fuel economy.

Model-free intelligent control of a 6-DOF Stewart-Gough based parallel manipulator

This paper illustrates an application of intelligent control to a 6-DOF Stewart-Gough based parallel manipulator. Under model free conditions, a three dimensional fuzzy PID controller is designed. The control is performed without using the forward kinematics of the manipulator. The performance of the fuzzy PID controller is compared against a linear PID controller. The fuzzy PID controller is shown to have better performance in tracking and higher robustness in load rejection than the linear PID controller.

A System for Providing Visual Feedback of Machine Faults

Machine faults and breakdowns are a concern for the manufacturing industry, especially in the field of assembly automation. There is a demand for diagnostic systems that can aid in minimizing downtime due to machine failure. Traditional methods for machine fault detection, such as PLC alarms, often provide limited useful information regarding the root cause of a machine fault. The project described in this paper attempts to enrich the quality of data available to technicians and engineers when diagnosing machine faults. The project goal is to develop an intelligent system that captures and saves video data of a fault occurrence. The proposed system was implemented on a laboratory conveyor apparatus and was qualitatively analyzed.

Optimal discrete sliding mode control with application

Presented is a study of a design methodology for sliding surfaces for single-input discrete-time sliding-mode control systems. A viable robust algorithm is detailed. The primary result is the optimal design of discrete-time sliding surfaces with respect to a linear-quadratic criterion. This case is considered for both the cheap control and general versions. The cheap control formulation results in an explicit sliding surface, whereas the general case requires an iterative solution. The control system is applied to a pulse-width-modulated gantry crane problem, showing the effectiveness of the design method.<<ETX>>