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Most manipulator motion controllers require joint velocity feedback. Whenever joint velocities are not measurable, they are estimated from the joint positions. However, ve-locity estimates tend to be inaccurate under low-speed motion or low sensor resolution conditions. Moreover, velocity estimators may either be susceptible to model uncertain-ties or introduce additional dynamics (e.g., phase lag) to the control loop. Consequently, direct substitution of velocity estimates into the controller results in the deterioration of the control peiformance and robustness margin. Therefore, this paper proposes a robust position-feedback motion controller which gets rid of the problems of uncompensated dy-namics and model uncertainties introduced by velocity estimators. Furthermore, a glob-ally asymptotically stable system, which is robust with respective to model parameter variations, is guaranteed. Theoretical analysis and experimental verifications are carried out. The results demonstrate that the proposed controller is robust and outperforms the conventional computed torque plus proportional integral differential (PID) controller. [ABSTRACT FROM AUTHOR]

Due to increasingly demanding requirements for driving safety, precise and robust control of tire traction forces is essential to implement high-performance vehicle-control systems. However, traditional slip-ratio-based methods cannot guarantee achievement of desired traction forces due to a lack of tire force feedback. This paper proposes an observer-based traction force control scheme that is robust with respect to variations of road conditions and tire model uncertainties. Moreover, achievement of desired traction forces is guaranteed. Simulation results verify the robust and satisfactory performance, even under suddenly changing road conditions, as well as parametric and nonparametric tire model uncertainties. [ABSTRACT FROM PUBLISHER]