Abstract
The dynamic performance evaluation of robots has proved difficult because of a lack of suitable measurement equipment. This thesis describes a novel instrument for the dynamic position measurement of industrial robots. The instrument consists of a retro-reflective target that may be attached to any point of the robot arm and two stationary measurement subsystems. Each sub-system generates a laser beam which follows the target. By simultaneously recording the positions of these beams and the distances from their centres to a known point on the target, sufficient information may be obtained for the subsequent off-line calculation of target position. A single measurement sub-system, which includes all of the components present within the complete instrument, has been designed, constructed and tested. Its optical, geometric and control requirements are discussed, and its interface to a micro-computer system is described. Both state-space methods and classical control techniques have been employed in the design of the controller; the unique features of which are its two modes of operation (distinguished by whether the system is tracking the target or not) and its ability to rapidly switch between them. Results are presented showing recordings of the end effector trajectory of a pneumatic point-to-point robot as it moves in a vertical plane at normal operating speeds. In addition, a precision servo-driven linear-motion device has been used for calibration purposes. These tests show that the instrument can record robot movements with speeds of up to 1.5m/s at a maximum sampling rate of 3.47kHz. Its accuracy (without signal averaging) is +0.7mm horizontally and +2.2mm vertically. Greater precision was not possible owing to problems of electrical interference within the circuitry of the prototype instrument.