Optimization Design Of Electromagnet For Electromagnetic Brake And Its Braking Control Circuit

The electromagnetic brake is a drum brakes by friction, which are mainly used on the trailer brake especially saloon cars, and achieves vehicle braking by translating the kinetic energy into the heat energy of the principle of electromagnetic resistance. At present, the research of the electromagnetic is still in its infancy stage. Based on the brake mechanism, the work posture and wear performance of the electromagnet are analyzed, and the unsymmetrical electromagnetic force is proposed to realize the even wear of the electromagnet surface and decrease the revolving tendency. The unsymmetrical magnetic circuit is designed by means of slotting. As the complex shape of the magnetic circuit, by using the electromagnetic analysis software Maxwell-3D for the simulation analysis, the simulation results amend the theoretical analysis to achieve the best unsymmetrical structures. Produced by this sample for the vehicle test, the results show that the working posture is steady, and card did not die and there did not find large fluctuations in friction. By wearing comparison of the symmetrical and unsymmetrical electromagnet, the testing result indicates that the unsymmetrical electromagnet obviously surpasses the symmetrical structure, which could enhance the life and the security of the brake, and meanwhile it is instructive for developing the electromagnet of different series of electromagnetic brake.On the basis of optimal design of the electromagnet, the test results of whole vehicle show that once the electromagnets work, the braking shoes would tightly cling to the wheels until the wheels were locked and sliding on the road, which would significantly enhance the non-security of travel, so it is necessary for effective braking control of the electromagnetic brake. The technology of PWM control is proposed that the braking torque output would be changed by the changing of the PWM signal duty cycle. According to the brake pedal for the entire control system of switching signals and the tractor deceleration as input signals, the braking control circuit of the whole vehicle will be completed including LM556 dual chip used to generate PWM signal timing, and other peripheral circuits. Through the circuit simulation with the help of the EDA software Multism, the designed PWM circuit could effectively implement different duty cycle of the PWM signal output, and satisfy the braking requirements of tractor-semi trailer.