This paper presents a method to measure gripping force of a bipedal wall-climbing robot (WCR) with spiny toe pads. The spiny toe pad is designed based on inspiration of an insect’s tarsal system. Each foot of the robot consists of a pair of opposed linear spiny arrays. The foot employs a pulley system to actuate the arrays via four pairs of tension and compression springs. Two Hall effect sensors are embedded into the robot feet to sense the gripping force by detecting the linear deformation of the springs. The two Hall effect sensors are calibrated and the relationship between the voltage signal output of the sensors and displacement is established before measuring gripping force. Then the consistency and accuracy of Hall effect sensor measurement method are verified by comparing with a commercial force sensor. A horizontal crawling test of the WCR is carried out and the gripping force verse time when the WCR moves. The experimental results show that the measured force history is in accordance with the actual movement states.

Magnetorhelogical (MR) dampers are gradually used in military devices for shock isolation and civil structures for suppressing earthquake-induced shaking and wind-induced vibrations because of their mechanical simplicity, high dynamic range, low power requirements, large force capacity and robustness. Since MR fluid dampers are energy-dissipating device, the issues of heat generation and dissipation is important. In this study, phenomenon of viscous heating and consequent temperature increase in a long-stroke MR damper are presented. In addition, a theoretical model is developed which predicts the temperature increase in the long-stroke MR damper. This model is solved numerically and a new coupling method was proposed to analyze the electromagnetic-thermal coupling problem on the basis of the mechanism of coupled field. Aim at the high frequency of piston head moving back and forth, as well as the changing current, the simulation model is established. The results show that the temperature effect on the damping force is significant and provide a theoretical basis and calculation method for the design and analysis of long-stroke MR damper.

The primary purpose of this paper is to provide a comprehensive review on the time delay of impact MR buffer system. The phenomenon of time delay which occurs in most of the MR buffer systems has been given little attentions especially in the applications where little time delay is demanded. Furthermore, the methods of reducing time delay have not been discussed in detail. So, in this study, several efforts have been made to decrease or even eliminate the phenomenon of time delay. Firstly, we analyzed two kinds of power supply sources and coil winding patterns. Next, an advanced correcting circuit was designed and the parameters of transfer function were determined by experimental data. The results show that, compared with the original circuit, it only takes 5ms to achieve 95% of the final state after correction, which increases 75% immediately. Furthermore, to evaluate the effect of compensation control strategy on time delay, the adaptive Smith compensation control was adopted and tested. Using the open on-off control strategy, four operating start times of current were applied, ranging from 0 to 300ms in increments of 100ms. The results show that the original maximum time delay is more than 150ms and it can be reduced to less than 50ms by adaptive smith compensation. Further analysis illustrates that decreasing time delay improves the dynamic performance of MRD in the buffer process, such as decreased overshoot, less fluctuation etc.

In the past decade, magnetorheological (MR) damper, as a new type of smart damper, has gained significant findings which have led to good applications in the field of engineering. However, most of these work focused on low velocity and low frequency applications. This study provides an experimental investigation into a self-designed MR damper subject to high impulsive load. First of all, the active force of the recoil system in weapons is selected as an impulsive input of the MR damper. Then, a MR damper with long stroke of 440mm and single-ended construction especially for impact and high velocity is designed. The novel recoil apparatus is mainly composed of a MR damper and a series of springs. The measurement system includes transducers and the corresponding signal process equipments. Under the firing impulsive load, three currents including 1.0A, 1.5A and 2.0A are investigated. The results show that the peak force becomes larger when the current increases. On the other hand, the MR fluid is uncontrollable when velocity rises rapidly and it is not controllable until 0.026s.