Development of a hydraulic robot for tunnel drilling : manipulator kinematics and tracking control
Zhong, George Guozhen
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The purpose of the research described in this thesis was to contribute to the analytical and experimental development of a new hydraulic tunnel drilling robot which could be used to replace the present tedious, but highly skilled manual operations, which must be carried out in dusty, damp, noisy and often dangerous conditions. In this research, three separate but related investigations were carried out by the author to improve the precision and speed of positioning the hydraulic robot and to reduce its cost. The first investigation was the determination of the kinematics of a new positioning mechanism which has a tripod arrangement of hydraulic cylinders to improve the positioning stiffness of the robot manipulator. The second investigation was the development and implementation of an optimal tracking control algorithm to improve the precision of the manipulator tracking. The third investigation was the design of a tracking control hydraulic system using a low cost stepping motor driven proportional valve incorporating a pressure compensator to stabilize the flow gain of the valve and automatically compensate for the load disturbances. The design considerations, theoretical analysis, (including the derivation and solution of the inverse kinematics problem) and experimental testing which were related to these three investigations are presented in this thesis. A kinematics model of the drilling robot manipulator was first established by deriving the homogeneous transformation matrices for describing the relationship between the links of the robot manipulator and its work space. A combination of analytical and numerical methods were then used to solve the inverse kinematics problem of the drilling robot manipulator. A three dimensional simulation was then developed to verify the validity of the solution of the inverse kinematics problem. To implement an optimal tracking control algorithm, the dynamics of an experimental hydraulic robot were analyzed and a multiple input fifth order discrete state space model was established for the pitch control hydraulic system of the robot. An optimal tracking control algorithm was then derived and experimentally implemented to improve the tracking precision and positioning speed of the pitch control system of the hydraulic robot. The design of the controller was based on the dynamic model of the hydraulic robot and the optimal tracking control algorithm. A Kalman filter was designed for observing the state variables of the system. System identification was carried out using a triangle pulse input method that was developed to estimate the parameters of the tracking control system. This method was faster and caused less disturbance to the positioning mechanism than the sine wave and the random signal methods. It also had the advantage of being able to estimate the parameters of the system for both directions of motion of the actuator. A hydraulic circuit, which used a stepping motor driven valve incorporating a pressure compensator to stabilize the flow gain of the valve and which automatically compensated for the load disturbances, was designed and tested in the pitch optimal tracking control system. The comparison of this hydraulic circuit with one using a conventional proportional valve showed that the former improved the tracking performance significantly under large load disturbances and could successfully be used in the robot optimal tracking control system for tracking the given trajectories of displacement, velocity, and acceleration.