Compared with the traditional spoke-type load cell structure, the biggest improvements of the new spoke-type load cell are:

(1) The mechanical processing method has been changed, and cutting processes such as drilling and milling are used to replace the complex and time-consuming wire cutting process. It not only improves work efficiency, but also ensures dimensional and surface accuracy, providing better process conditions for subsequent surface treatment of the wheel spoke strain zone and pasting of shear resistance strain gauges.

(2) Due to the use of cutting processes such as drilling and milling, the upper, lower, left and right sides of the spokes (actually strain beams fixed at both ends) have arc structures, which increases the root stiffness and reduces the hysteresis error. Because under the action of compressive load, the sinking of the wheel hub drives the wheel spokes to deform in an approximate parallelogram shape, causing the two pairs (four) of wheel spokes and the part of the wheel hoop connected to them to protrude outward and deform. This creates a moment that moves outward. The greater the stiffness of the wheel hoop and hub, the smaller the displacement of outward and inward deformation, the shorter the action time of bottom friction, the shorter the time for blocking the spokes to return to their original state, and the smaller the hysteresis error.

(3) From a mechanical perspective, due to the increased stiffness of the hub and wheel hoop roots, the spokes can be regarded as embedded in the wheel hub and wheel hoop. It cannot rotate freely under the action of external load, that is, the rotation angle is zero, but the spoke deforms under the action of shear force, so its deflection is not zero, which creates conditions for establishing a scientific and reasonable mechanical model.

2 .Mechanical model and theoretical calculation of the new spoke-type load cell

The new spoke-type load cell consists of a hub that bears and transmits load, a hoop that bears the load in a circumferential direction, and two pairs or four spokes. After the wheel hub is acted upon by an external force, a pair of principal stresses and principal strains of tension and compression are generated in the center of each spoke. Single shear resistance strain gauges are pasted on both sides of the center of each spoke to measure the shear strain. Due to the different pasting directions of the resistance strain gauge sensitive grid, strain values of equal magnitude and opposite directions are produced, which fully meets the conditions for forming a Wheatstone bridge circuit.