Optimal Control of Screw In-pipe Inspection Robot with Controllable Pitch Rate

Abstract

A Steerable in-pipe inspection robot is designed in this paper and its optimal control based on linear quadratic regulator (LQR) approach is performed subject to input minimization. In-pipe inspection robots are necessary mobile robots in order to investigate the pipelines. Most of the in-pipe inspection robots are limited to move with a constant pitch rate. An in pipe inspection robot is proposed in this paper which is based on screw locomotion and its steering angle is also controllable in order to handle the pitch rate of the movement and bypass the probable obstacles. Since the proposed robot is multivariable with more than one controlling input, minimizing its control inputs are extremely useful. The goal of this paper is to extract the dynamic model of the mentioned steerable screw in-pipe inspection robot and controlling it within a predefined trajectory in an optimal way. The proper mechanism is designed and its related kinematics and kinetics are derived. Afterwards the objective function is defined based on minimizing the controlling input and maximizing the accuracy of movement. The nonlinear state space is linearized around its operating point and optimization is implemented using Linear Quadratic Regulator (LQR). The efficiency of the designed robot and controller and the optimality of its controlling procedure are investigated by the aid of MATLAB simulation and comparative analysis. It is proved that the designed robot is able to move with controllable pitch rate and acceptable accuracy while the obstacles can be avoided and the energy consumption is optimized. At the end the validity of modeling and simulation in MATLAB is also verified by modeling the robot in ADAMS and comparing the results.

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