A New Method for Sewing Machine Starting Based on BLDCM
A New Method for Sewing Machine Starting Based on BLDCM
According to the characteristics of the sewing machine, a new starting method was presented on the basis of the analysis on the characteristics of application of brushless DC motor, which is the three-step starting technique during the sewing machine starting. The experimental results indicate that this method significantly enhances the speed of starting and improves the reliability of the equipment, as well as more adaptive performance and better in dynamic response.
Brushless direct current motor (BLDCM) to have the volume to be small, the movement is reliable, the control precision is high as well as maintenance convenience merits and so on, simultaneously also have characteristics that is the efficiency to be high and the velocity is easy to be adapt[1]. In recent years, along with the modern electronic technology's fast development, this kind of motor already widely applied in the industrial field. The brushless direct current motor more and more to be used in the sewing machine manufacturing industry. At present, the Brushless direct current motor's control mode to have many kinds, the classics PID control, afterward presented the auto-adapted fuzzy PID control, as well as other advanced control method [4]. Regarding the sewing machine, the starting time can be changed during the motor startup, based on this adjust, simultaneously it requested that the motor have no the over modulation basically and fast stable. The present control method is not very ideal.This article according to the control mode of brushless direct current motor as well as the sewing machine to electrical machinery's characteristics that the start time is requested, uses three step of start methods, the soft initialization mode is used in the first starting period, the PI adjustment is used in the second starting period and changes the acceleration, uses the PID adjustment in the final starting period, in which pre-treats the over modulation, the controller completes the motor from the start to the stability. Starting time's adjustment may be carry on in the starting period. The experimental result indicated that the system’s starting ability and the dynamic response performance is good by using this method. The running effect is also satisfactory.The brushless direct current motor's rotational speed formula is (1). Φ−='/)(PKIdRUdN (1)N is the direct current motor rotational speed, K ' is the motor constant, Φ is the electrical machinery air gap synthesizes the magnetic flux, P is the electrical machinery pole number, Ud is armature voltage, Id is the armature current, R is the armature coil resistance[5]. The brushless direct current motor's velocity modulation performance is same as the direct current motor, namely the motor’s velocity is modulated by changing the motor’s armature voltage, or the exciting current is changed. Obtains the motor velocity feedback value according to the motor’s positional information, compares with the given value, then changes the three-phase PWM output through the controller, realizes the velocity’s control. Along with the motor position's difference, the signal which the position sensor produces is also different, these signals after processing uses for to control the bridge correctly, thus change the PWM value, namely control the direct current motor rotational speed.VS Sewing Machines
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At present, the PID parameter installation method research is domestic, like phase angle allowance installation algorithm, neural network PID algorithm, as well as heredity optimization PID algorithm and so on. These methods may enable the system performance to have the improvement, but design process complex tedious, the practical application is restricted. In fact the PI controller is widely used in control system because its structure simple, and it is easy to realize, the reliability to be high. However, there are contradictory in the rapidity and the over target by using PI control policy [8] [9]. Uses the pulse width velocity modulation, when PWM is changed, the control voltage is changed, the converter outputs the average voltage according to the linear rule change, but its response is late. Therefore the PWM system may also regard as is a delay component, so the velocity of the motor and starting time is control hardly. This paper uses three steps that the control voltage is changed by different control’s mode [10]. The starting time can be changed in the second step. B.First step P control In the first step, the acceleration period may carry on the open-loop control, causes the motor slow start by constant acceleration. When arrives at the preinstall definite value, entered the stable velocity modulation stage. The value of PWM is changed in the proportionate mode before the brushless direct current motor rotating, which time is short. 0*dkd= (2)Which d is the data of PWM register, k is proportion, 0d is the register’s first data that be given by the system. The first step control mode is over when motor starts to rotate. The velocity of motor is slow during P control mode. The velocity of motor can be changed from zero to the motor start to rotate. The other installments of sewing machine can be protected during the first step [11]. If k is small, then the starting time value is small, and if k is big, the starting time value is big. C.Second step PI control In order to reduce the over modulation, firstly, reduces the PWM value, which the PWM value is equal to d-d*5%. Secondly, according to the brushless direct current motor's start and the velocity modulation characteristic, this article uses PI control method during the second step period. For the PWM value is changed fast, and the motor velocity changes slowly, as well as obtains the velocity is slow than the PWM value. The proportion value is small, and the PWM value is changed slowly when the obtained velocity is close to the given velocity.
