Researches On Testing System For Gimbal's Micro-torque Of Steering Tube

With the rapid development of modern automobile industry, people have higher requirements of its dynamics, comfort and security. Security has become the critical focus in the tendency of China's automobile technology development. Rover750 steering tube is designed based on the concept of passive safety technology. The design of its collapsible energy-absorbing structure and deformation element in the tube with gimbal can effectively reduce impact of the steering wheel to the drivers on emergency, which makes the steering system more safe.One of performance evaluations to this new type of steering tube is to measure its gimbal's micro-torque. Gimbals can move in two different planes. When measured in one plane, the gimbal must be kept stable in the other one. The traditional measurement method keeps the gimbal stable by spring hook, however, it introduces variable outside force and produces errors to the results which cannot be eliminated.Two new practical methods named Elbow Method and Magnetic Suspend Method are presented. The former one keeps the gimbal stable directly by the force sensor, which can endure a certain range of shear force and be non-sensitive to this force. Similar to Maglev Train, the other method keeps the gimbal by magnetic repulsion. Both of the methods achieve the goals and avoid the disadvantages of traditional method.The automatic testing system of gimbal's micro-torque according to the Elbow Method is discussed in detail. Firstly, the mechanical characteristics of the system is described, which can move freely in three different coordinates and avoid clamp locking when measured. The testing system controls the electromotor with the core of industrial controlcomputer to realize the completely automatic testing of gimbal's micro-torque depended on high precision force sensor, signal processing circuit, and PCL-818L data acquisition card of ISA bus. Compared with the traditional method, the testing data proves the validity and effectiveness of Elbow Method, and high precision, efficiency and powerful data operation and processing of the system. Since being put into production use, the system is always in good state and promotes the production efficiency greatly.The software is also discussed, especially on its parts of precise timing, digital data filtering, real-time curve drawing and automatic interface response in the VC programming.