The Design Of Sensorless BLDCM Control System For Ventilator

With people’s living standards improving, More and more people are sufferingfrom obstructive sleep apnea syndrome(OSAS) which impacts on the quality of lifeand even endangers the life. The most of patients are male who are obese. Using theventilator is the most effective way to treat the disease, so good low-cost developmentof ventilator has a good practical significance. This paper successfully realized asensorless BLDCM control system which used BLDCM Driver IC ML4425as adedicated control chip, the microprocessor AT91M5580auxiliary speed control, anddiscussed a ventilator’s driver source code Component model.Firstly,this paper introduces the BLDCM and the development of the BLDCMand embedded component technology. According to the specific requirements of aportable ventilator, the paper chosen ASIC controller ML4425as the controller ofBLDCM. Followed analyzed the structure，working principle，a mathematical modeland operation of properties of BLDCM. in detail. Then analyzed deeply theprinciple of back-EMF method which the ML4425used.The hardware of the control system consist of the linear regulator circuit,ML4425external circuit, three-phase power bridge drive circuit and protection circuit.The ML4425external circuit and three-phase power bridge drive circuit are the coreof the hardware circuit which realized the motor’s start, rotor position detection,speedcontrol, current commutation, braking,and current limit protection and so on. Itdescribed in detail the design of the important parts of the circuit components andparameters choice. Then combination of hardware problems encountered duringcommissioning, summed up the some debugging techniques of the ML4425. Insoftware design, it adapted the variable speed PID algorithm in order to regulatespeed smoothly. This paper describes the design of subroutines of software. In orderto achieve that using the method of component to develop the follow-up ventilator, itdesigns a ventilator driven componet model. The model definition, the logical modeland the three operations was given in the paper,. Then it used the model to achieve themotor drive components.Finally, the control system is tested after debugging the hardware and software,through experiment wave and data, the performance of the control system is verified,meeting the requirement of the control system.