With the advantages of high resolution, structural simplicity, reliability, compact size, and high sensitivity, inductive sensors have been widely used in nanopositioning systems. However, the measuring range of traditional inductive sensors are usually limited to 0.2 mm. A novel analysis and design methodology of the miniaturized inductive sensor with large measuring range and nanoscale resolution is proposed. Firstly, an accurate leakage inductance model is established. Secondly, a design rule of armature size is proposed by considering the fringing effect. Then, the error terms introduced by the measurement circuit of differential inductive sensors are analyzed and the corresponding error suppression methods are illustrated. Moreover, A design rule of selecting the optimal excitation frequency is proposed to meet the requirements of high Q value and high bandwidth, and to minimize the impact of core loss resistance on the performance of the sensor. Validated by the experiments, the proposed analysis and design method can effectively guide the design of the miniaturized inductive sensor with nanoscale resolution in the measuring range of ±0.5 mm. The overall size of the fabricated sensor prototypes is less than 6 mm × 6 mm × 3 mm. Combined with large range, high resolution and ideal miniaturization, this inductive sensor can be well suitable for compact and large stroke nanopositioning systems.

In the UAV electro-optical pod of the two-axis four-gimbal, the characteristics of a coarse–fine composite structure and the complexity of dynamics modeling affect the entire system’s high precision control performance. The core goal of this paper is to solve the high precision control of a two-axis four-gimbal electro-optical pod through dynamic modeling and theoretical study. In response to this problem, we used finite element analysis (FEA) and stress study of the key component to design the structure. The gimbals adopt the aerospace material 7075-t3510 aluminum alloy in order to meet the requirements of an ultralight weight of less than 1 kg. According to the Euler rigid body dynamics model, the transmission path and kinematics coupling compensation matrix between the two-axis four-gimbal structures are obtained. The coarse–fine composite self-correction drive equation in the Cartesian system is derived to solve the pre-selection and check problem of the mechatronic under high-precision control. Finally, the modeling method is substituted into the disturbance observer (DOB) disturbance suppression experiment, which can monitor and compensate for the motion coupling between gimbal structures in real time. Results show that the disturbance suppression impact of the DOB method with dynamics model is increased by up to 90% compared to PID (Proportion Integration Differentiation method) and is 25% better than the traditional DOB method.

Precise cable drive is a flexible frictional transmission method that transmits power from drive capstans to driven pulleys by a properly preloaded transmission medium. Since most of precise cable drive mechanism with high pointing precision proposed in previous studies suffer from low transmission stiffness and small output torque, this paper presents a novel many-to-one configuration precise cable drive mechanism (MCCDM) with high precision and large torque. The design methods of many-to-one configuration are studied including the system optimal design and cable wrapping design. The transmission characteristics of the developed configuration are analyzed, considering transmission capacity, transmission backlash, and transmission stiffness. The corresponding parameter sensitivities are also investigated. Moreover, a prototype of the MCCDM has been built, with which a series of experiments are carried out. It is noted that the developed mechanism has a motion range of ±2 rad. The steady-state error to a step reference of 1 rad amplitude is only 1.39 µrad and the position resolution is better than 0.5 µrad. This mechanism could achieve maximum output torque of 35 Nċm with compact size and light weight. It has reached a considerable toque-to-weight ratio of 8.997 N·m/kg. The experimental results show that the self-excited oscillation and backlash are dominant nonlinear effects in the MCCDM system. It shows that the self-excited oscillation is a function of the rotational displacement in such a system, with the highest peak at 0.1669 cycle/mrad and the amplitude of 34.63 µrad. The backlash could be measured about 60 µrad under exciting of a small amplitude and low frequency sinusoidal signal. The proposed technologies could have strong technological implications in some special applications such as antenna servo system.

Coarse–fine composite mechatronic systems face numerous challenges due to the structural complexity and diversification of multi-gimbals. The core goal of this manuscript is to address the issue of the coarse-fine composite mechatronic system stability of a UAV (unmanned aerial vehicle) multi-gimbal electro-optical pod using USM-VCM (ultrasonic motor and voice coil motor) mechatronic design, Euler dynamics modeling, and stability DOB (disturbance observer) control. In response to this problem, a Hall effect electromagnetic circuit and USM-VCM drive acquisition circuit are designed. A Euler dynamics model in the Cartesian coordinate system is built to derive the kinematics coupling compensation matrix and mechanical parameter optimization method between the gimbals. Finally, the model is substituted into the DOB suppression control, which can monitor and compensate the motion coupling between the coarse–fine composite mechatronic systems in real time. Results show that the disturbance suppression impact of the DOB method with the Euler optimization model and USM-VCM mechatronic design is increased by up to 90% compared to the PID (proportion integration differentiation) method and 20% better than the traditional DOB method.

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