The flexure joints are proposed to replace the rigid assembly between the cross-arm and the moving carriages of dual-drive H-type gantry (DHG) for higher reliability and fine rotational alignments. In the literature, the flexure joint of the DHG is modeled as an ideal linear torsional spring, resulting in an inaccurate estimation of the cross-arm’s angle. In this study, a generalized analytical kinetostatic model of flexure-linked DHG is built by considering the geometric nonlinearities. The expressions of beam coefficients in the model are obtained from either beam constraint model (BCM) or Timoshenko BCM (TBCM) according to the given criterion of length-to-thickness ratio. The model is capable to accurately estimate any two variables among the rotation angle of the cross-arm, the misalignment of two carriages, and the net driving force, as long as the other is known. Simulations and experiments on the testbed validate the accuracy and show practical appeals of the proposed model.

Robotic manipulators are complex and dynamic nonlinear mechanical systems subject to numerous uncertainties, such as payload variations, frictions, and unmodeled dynamics. To mitigate the uncertainty caused by these disturbances and minimize the tracking errors of the controllers, this study proposed a finite time tracking-based controller (FTC) that embeds a (NDO) and a second-order sliding-mode modifier (SOSM). The NDO was incorporated to compensate for the system’s global bounded uncertainty and the SOSM used a robust nonsingular terminal sliding-mode modifier to stabilize the controller. The theoretical analysis showed that the tracking error could quickly converge in finite time. Simulation on a typical robotics manipulator demonstrated the practical appeal of the proposed scheme.

The current treatment of otitis media with effusion (OME) when medication fails is to surgically insert a grommet tube in the tympanic membrane. A novel precision surgical device has been developed, which allows tube insertion to be accomplished in an office setting. The device leverages on a piezoelectric ultrasonic motor (USM) stage to facilitate the motion sequences for the procedures. The core engine of the device is in the USM motion controller to achieve the high precision, fast response, and repeatability necessary to allow these medical procedures to be efficiently and successfully done with minimum trauma to the patient. This paper focuses on the controller design for the USM to meet the unique set of specifications to apply the surgical device optimally on patient with OME. A model of the USM is first built and identified. A proportional-integral-derivative (PID) controller is used as the main tracking controller with the parameters derived optimally using an linear-quadratic regulator (LQR)-assisted tuning approach. A sign function compensator acts to remove nonlinear dynamics due mainly to friction and a sliding mode controller further rejects remnant uncertainty and disturbance. The experimental results show that the constituent control components fulfill their respective functions well, and collectively, the composite controller is effective toward delivering the level of control performance to meet the objectives for the medical procedures.