Simulation and Experimental Research on the Disturbance Behavior of a Sun-Tracking Solar Array Driven by a Stepping Motor

A sun-tracking solar array is an effective solution to the increasing energy demand of spacecrafts. However, the driving torque fluctuation of the solar array driving assembly (SADA) and its oscillatory motion lead to the micro-vibration problem of the spacecraft. In this article, a disturbance torque model of the sun-tracking solar array, which takes its friction and flexibility into consideration, is established. Furthermore, a test platform was built to measure the disturbance force/torque, and a solar array simulator (SAS) was designed to replace the solar array in the ground experiments. Finally, the disturbance torque of the SADA-driven SAS is simulated, and the model is validated by comparing the simulation results with the experimental results. These results show that the frequency error of the model is less than 0.648%, and the amplitude error of the corresponding frequency is less than 22.33%, which indicates that the proposed model can effectively predict the disturbance torque generated by the sun-tracking solar array in orbit. The research provides theoretical guidance for the system optimization design and micro-vibration suppression of spacecrafts.

Algorithm for the torque sensorless worm gearbox servo application based on kinetic motion/friction realization

This paper provides an effective systematic procedure for the efficient treatment of worm gearboxes for industrial-grade cases. The accurate and general dynamic model of the worm gearbox is analytically obtained and the effects of the dominant factors, such as the disturbance torque and friction between the teeth and threads, are also addressed. A universal algorithm is proposed for accurate estimation of the disturbance torque that makes no utilization of any designated sensing unit. Numerous experimentations have been conducted to validate the proposed procedure and algorithm. The contributions of this paper are not limited to worm gearboxes but rather are extendable to all other conventional gearboxes that use similar power transmission methods. The gradient patterns of the normal force, the friction force, and the coefficient of friction in worm gearboxes are also identified as a function of the effective elements, such as the output loading torque and angular velocity.

Measurement of frequency characteristics of disturbance torque in the process of satellite antenna rotation

As an important equipment for satellite signal reception and transmission, the satellite antenna needs to be rotated in real time to achieve real-time tracking of the target and complete signal transmission during applications. Antenna driving mechanism is generally composed of motor and other components, which will cause some structural vibration during rotation. For high-stability satellite applications, the vibration disturbance torque is a major factor affecting the satellite stability. In order to study characteristics of the disturbance torque, the disturbance data from the antenna under different rotation conditions should be measured. In this paper, the frequency characteristics of disturbance torque of a rotating satellite antenna using stepper motor as driving motor is tested and discussed.

Super-twisting algorithm with fast super-twisting disturbance observer for steer-by-wire vehicles

The control performance of a vehicle steer-by-wire (SBW) system can be seriously affected by vagaries of tyre-road conditions and external disturbance. Aiming at the problem of fast estimating and compensating the time-varying disturbance torque acting on the front wheels under different working conditions, this article presents a super-twisting algorithm (STA) combined with fast super-twisting disturbance observer (FSTDO) control scheme. At first the SBW system is modelled according to the experiment plant. Secondly, the FSTDO is designed according to SBW system model. A fast reaching law is adopted to accelerate the sliding variable convergence rate and enhance the response speed of the observer. The FSTDO-STA controller adopts STA control in closed-loop system. The control signal is continuous, so that, the chattering could be inhibited. The stability of FSTDO error dynamics and closed-loop dynamics is proved in the sense of Lyapunov. Finally, comparative verification experiments are carried out to demonstrate the validity of FSTDO-STA. The FSTDO-STA controller can quickly estimate and compensate disturbance torque under various operating conditions. Compared with other comparative algorithms, the proposed controller has some advantages in response speed, control accuracy and robustness. And it was corroborated by the experimental results.

Halt Optimization Strategy for a Space Manipulator with a Joint-Locked Failure

Aiming at a space manipulator with a joint-locked failure, a halt optimization strategy is proposed in this paper. Firstly, a halt configuration optimization model (HCOM) is constructed, to select an optimal configuration where the kinematic ability of the manipulator is the best. Secondly, considering the constraint of joint running parameters and the disturbance torque of the base, we construct and solve the halt motion optimization model (HMOM), which can achieve a steady halt and ensure the safety of the manipulator. The correctness and effectiveness of the proposed strategy in this paper are verified with a 7-DOF space manipulator. This strategy firstly puts forward the idea of halt configuration optimization and realizes the minimum global disturbance torque of the base in the halt process.