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Field and Service Robotics - Corke P. and Sukkarieh S.(Eds) Part 13

Tham khảo tài liệu 'field and service robotics - corke p. and sukkarieh s.(eds) part 13', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 486 T.M. Howard and A. Kelly 4.1 Rocky 7 Rate Kinematics Actuator Dynamics and Wheel Slip The Rocky 7 rover has eight actuators a steering actuator on each of the front two wheels and six drivable wheels. In order to get a realistic model of actuator dynamics a first-order lag was assumed. vco t t t - vco t t - T vco t t - T 17 1 2out t -T t - t - T t - T 18 The wheel slip model assumes that only a fraction of the requested velocity is achieved. Inverse rate kinematics generate the achieved Vout out due to the actuator dynamics and wheel slip model. 4.2 Rocky 7 Suspension Kinematics Just as in the general solution the suspension model provides a mapping of the linear and angular velocities estimated by the actuator dynamics and wheel slip models from the body frame to the world frame except now the suspension model is known. Taking advantage of the fact that there are six controls attitude ớ altitude z and the three rocker-bogie angles p 2 and six constraints zC1 -zc6 the same numerical method used in the inverse trajectory generation solver is applied. An error vector Az AzC1 Azc6 T is formed from the difference between the elevation of the terrain and the contact point of each of the six wheels. The initial guess of control is adjusted by the product of the inverse Jacobian of the forward kinematics of the contact points with respect to the world frame and the elevation error vector until the terminal conditions are met. 4.3 Rocky 7 Kinetic Motion Model Since the Rocky 7 rover is a terrain-following mobile robot the kinetic model follows the form of equation 13 . The attitude and altitude are determined from the suspension model for a given pose. 4.4 Rocky 7 Trajectory Kinematics The forward model of trajectory generation for the Rocky 7 rover is generated by integrating equation 13 . Trajectory Generation on Rough Terrain Considering Actuator Dynamics 5 Implementation 487 5.1 Forward Solution of Trajectory Kinematics In order to determine the terminal pose xf yf