Realization of DC Motor Drive and Low Speed Control
【Abstract】 DC motor is widely used as an actuator in control system. This paper analyzes the hardware driving method of DC motor, and puts forward the speed regulation method of DC motor in low speed operation. The method uses the 51 series MCU as the control core, in the peripheral of the controller supplemented by the necessary hardware circuit, adopt the software and the hardware union work way. Experiments show that the DC motor speed control method is simple and feasible, and expand the DC motor speed range, to achieve the desired results.
Key words: DC motor; drive; low speed control; PWM
Motor is the control system commonly used in the implementing agencies, small DC motor because of its low price and has been widely used. The current market, the DC motor sold in addition to the motor, the general speed is relatively high, when the supply voltage reaches a certain value ("threshold") can be activated, and the motor once started, the speed is very fast. Although the DC motor has a good adjustment characteristics (motor speed and power supply voltage is proportional), but the prerequisite is that the motor has been normal start. In the actual control system often need a wide range of speed, such as intelligent car control, in addition to its higher speed section of the speed control, the low-speed section of the control is also extremely important. Therefore, based on the analysis of several DC motor hardware driving methods, this paper puts forward the method of low speed control of DC motor and experiments with the problem of low speed control and low control range of DC motor.
2. DC motor drive circuit
DC motor hardware drive circuit many types, of which the most common are economical drive, T-bridge drive and H bridge drive a total of three.
2.1 Economical drive
The drive method uses only one switch tube (Darlington transistor or MOS tube) to complete the drive, through the control switch off to turn on or off the motor, the drive circuit shown in Figure 1. The advantage is the use of less switching elements, the circuit is simple, low cost, you can achieve a simple speed, one end of the motor ground, easy to lead to feedback signal. The disadvantage is that only one-way rotation of the motor can be controlled.
2.2 T-shaped bridge drive
T-shaped bridge drive mode using two switches to complete the drive, through the control switch off the circuit can be achieved reversible power supply to achieve forward and reverse rotation control, the drive circuit shown in Figure 2. When SW1 is on, motor M is subjected to forward voltage (forward); when SW2 is on, motor M is subjected to reverse voltage (reverse). The advantage is the use of less switching elements, low cost, simple circuit, can achieve the motor forward and reverse control, the motor at one end of the ground, easy to lead to feedback signal. The disadvantage is the need for positive and negative polarity power supply, triode or MOS tube to withstand twice the supply voltage.