Study Of Brake Inertia Dynamometer Measure And Control System

Inertia dynamometer test is the most authoritative test in evaluating thefriction behavior of brake linings since the real braking process can be simulated onit. In order to simulate this process, Inertia dynamometer is often designed as anintegrated system involving central measuring and control system, mechanicalsystem, hydraulic and pneumatic system plus cooling and cleaning system, sincetoo many test items are involved while there is no uniform test standard. However,domestic inertia dynamometer as a whole stands in a low control level, whichdepresses the authenticity of brake performance evaluation. On the meantime,imported machines are extremely expensive, the price of which are several times asexpensive. It is urgent to develop high performance inertia dynamometer withindependent property right.In this paper, a practical inertia dynamometer measurement and control systemis developed, aiming at making up the weak point of domestic control system. 590+controller is employed as the center of speed-current dual loop speed controlsystem. A wireless signal transmission apparatus is designed on purpose to measurethe temperature of the rotating brake drum. Hydraulic servo control subsystemgives a best solution for tube pressure control as well as constant torque control. Alinear interpolation way is proposed to deal with the nonlinear characteristics ofblower and proved to be an effective way. This measurement and control systemgives an optimistic performance when employed in FAW.It is always intractable to debug inertia dynamometer on the spot. Interferencefrom blower transducer once spoiled the remote temperature transmitting system aswell as analog signal collecting system. It was eventually eliminated by fixingpower filter and load filter. (Hydraulic power transducer was omitted since it wasfixed in the inner mainframe) Both of speed and torque control system adopt PIcontroller. Experience and patience are needed to adjust P&I parameter as thehydraulic apparatus are rather fragile. Under the assistance of Mr. Liu and Mr. Tao,adjusting law was finally in my hand and these controllers began to work smoothly.Influenced by the shape and material of pipe, the function between wind speed ofblower and setting frequency is often nonlinear and hard to establish. A partitionlinear interpolation method is advanced in this paper to control wind speed. Windspeed at different frequencies must be scaled first. Adjacent points then connectedas linear processing. When measuring point is large enough, the curve we have ismuch similar to the real one. The number of measuring point can be decidedaccording to the accuracy order. In this paper, 9 points are selected. Thespeed-frequency curve is shown in the following chart. Application in the inertiadynamometer proves it to be an effective way to control wind speed.When flywheel is the sole simulator, we often get discontinuous inertia,whereas hybrid simulation by flywheel and motor can always meet our desire. Inthis paper, inertia simulation by controlling motor torque and shaft speed ismodeled and simulated. Torque control has an advantage of short adjusting time,which gives a fast torque response. This method does not need initialization sincethe brake torque keeps constant when brake is applied no matter how much systeminertia is. However, the apply time of electrical inertia must be determinedbeforehand. Speed error can easily be eliminated by PI controller when speedcontrol is employed. Robustness of speed control method extrudes when loadchanges. However, drive speed loops are typically too sluggish if the controller is apure speed-current dual loop system. One usual way is to forecast the tendency ofspeed. A fast speed reacting system can be achieved by using speed feed forward,the value of which can be calculated by the electrical inertia controller using ratedspeed and power of driving motor and current speed. Flywheel-inertia andelectrical-inertia hybrid simulation takes flywheel-inertia as the main part andelectrical-inertia as accurate adjustment thus tides over the shortage of both pureflywheel inertia simulation and pure electrical inertia simulation. This method canadjust inertia continuously while reduce power dissipation, motor powerrequirement and control level. Inertia hybrid simulation is proved to be feasible byanalyzing the simulation curve.