Contact force sensing is necessary for robots to safely grasp and improve walking performance. Motivated by the linkage-type geometry of robotic fingers and legs, this article realizes contact force sensing on the L-shaped structure without additional force sensors. The lever-type method of strain exposure (LTMSE) is developed to enhance the force-sensing performance. This method is able to reduce the coupling in three-axis force measurement and improve the tradeoff (between sensitivity and stiffness). Further decrease of the coupling is accomplished via appropriate strain-gauge arrangement and static decoupling algorithms. The experimental results have demonstrated the force sensing performance of the L-shaped structure and verified the feasibility of the LTMSE for three-axis force measurement. The proposed design has potential applications in linkage-shaped robotic fingers, legs, and probes.

This paper presents the design and development of a new type of planetary traction drive bearing-type reducer. In this design, the transmission outer ring is replaced with an elastic ring. The design constructs a circular arc at the axial end of the rolling body’s contour line. This ensures that the contact point of this arc with the reducer’s outer ring and the inner ring’s axial end face is maintained on the radial traction contact line. As a result, it can replace the thrust bearing and provide an axial support function. It has the advantages of simple structure, easy processing, smooth transmission, and low noise. This paper first introduces the design and development process of this bearing-type reducer and presents systematic research on its transmission principle and dynamics. Subsequently, in response to the edge effect phenomenon of the outer ring contact line, the contour line of the outer ring is refined by adopting the shaping method used for bearing rollers, establishing a full circular arc profile shaping method, which significantly improves its edge effect. Finally, in our investigations, combined with experimental tests, a prototype of the bearing-type reducer was fabricated, and the speed ratio, torque, and transmission efficiency of the reducer were studied. The results demonstrate that the bearing-type reducer can achieve high transmission accuracy and efficiency. The transmission performance varies significantly under different lubrication conditions, with the peak efficiency reaching as high as 99.97% when using Santotrac 50 traction oil. The results verify the feasibility of the proposed design method and have the potential to be applied in wheel hub motors and robot joints.

This article presents a wheel force sensing method based on spherical-joint force measurement. The force measurement uses strain gauges on L-shaped linkages connecting the wheel to the double wishbone suspension system. It does not require the wireless power supply and signal transmission because it does not rotate with the wheel. Using the measured joint-forces to solve the suspension mechanism configuration, the wheel position and orientation (relative to the vehicle) can be calculated, eliminating the need for position sensors. Through the continuous calculation of the position and orientation, the inertia force and moment can be estimated, which is used in the Newton-Euler formulation for wheel force calculation. Experimental results show the root mean square error of three-axis wheel forces ≤8.26 N and mean error of three-axis wheel forces ≤4.06 N, which validates the feasibility of the proposed method.