Xiaozhi Zhang

This paper presents an adaptive sliding mode control (ASMC) scheme based on strain gauge position feedback for compensating for motion errors in a piezoelectric nanopositioning stages and ensures precise and reliable motion tracking control. The innovation of this scheme lies in calibrating the relationship between the feedback voltage of the strain gauge and the actual stage displacement. Thus, the calibrated feedback displacement is directly used as the position feedback signal for the ASMC scheme. Adaptive rules are employed to adjust the control gains, thereby eliminating the requirement to determine the upper bound of the disturbance. The stability of the ASMC strategy is theoretically proven within the Lyapunov framework. Comparative experiments under external disturbances have confirmed the superiority of the proposed control scheme. Results demonstrate that the proposed control scheme exhibits superior robust tracking performance compared to the traditional sliding mode control (SMC) scheme.

This paper presents the design of a sliding mode controller to compensate hysteresis nonlinearity and achieve precision motion tracking for a novel piezoelectric tip/tilt platform driven by a PZT actuator. The sliding mode control scheme is based on the unique physical characteristics of the piezoelectric tip/tilt platform. The proposed scheme effectively guides the platform state onto a predefined sliding surface and ensures its sustained movement along this manifold. This approach reduces tracking errors compared to conventional methodologies. The stability of the sliding mode control scheme is demonstrated by the Lyapunov theory framework. It achieves precise motion control with minimal tracking error on a piezoelectric tip/tilt platform. The properties of the controller have been confirmed through experimental tests. The proposed control scheme enhances the robust tracking and stability performance on the piezoelectric tip/tilt platform, outperforming traditional control schemes. Compared with the P562.6CD produced by PI Germany, the proposed innovative approach not only boosts the platform’s resolution by 32% but also implements a 33% reduction in cost.

This paper presents the design, analysis and testing of a novel three-degree-of-freedom (3-DOF) parallel-kinematic constant-force end-effector. The constant-force end-effector enables a safe interaction between the end-effector and contacted object. To obtain the constant-force property without extra fixing support, the symmetrical bistable flexure hinges are adopted. Then, to reduce the constant-force value, a preloading constant-force mechanism is introduced. The parallel-kinematic mechanism based on flexure hinges is constructed to decouple the 3-DOF motion. FEA simulation study is conducted to investigate the constant-force property and the decoupling ratio of the designed mechanism. Moreover, a prototype is fabricated and experimental testing is conducted to verify the performance of the constant-force mechanism.

This paper presents the design and testing of a novel flexure-based compliant compound constant-force mechanism (CCFM). One uniqueness of the proposed mechanism lies in that it achieves both constant-force input and constant-force output, which is enabled by integrating two types of sub-mechanisms termed active and passive constant-force structures, respectively. Unlike conventional structures, the active constant-force structure allows the reduction on input force requirement and thus the enlargement of motion stroke provided that the maximum stress of the material is within allowable value. While the passive one offers a safe environmental interaction during the contact process. Analytical model of the proposed CCFM is derived which is verified by simulation study with finite element analysis (FEA). A prototype mechanism is fabricated by a 3D printer to demonstrate the performance of the proposed CCFM design. Experimental results reveal the effectiveness of the reported CCFM.

This paper presents the design and analysis of a new compliant constant-force gripper based on compound constant-force mechanism. The constant-force property can reduce the input force and prevent the object from damage without using a force feedback control. The compound constant-force mechanism contains an active and a passive constant-force structure. The active constant-force structure can reduce the input force, while the passive constant-force structure offers the safe interaction during the gripping operation. To evaluate the performance of the compound constant-force mechanism, analytical modeling is carried out, which is verified by conducting finite element analysis (FEA) simulation study. Results demonstrate the promising performance of the proposed mechanism design.