CN100448156C - Brake control method and system of direct-current brushed motor without Hall assembly - Google Patents

Abstract

The invention provides a brake control method and system of a direct-current brush motor without a Hall assembly. When the system is started, the motor is braked in advance to detect and record the static armature current value when the motor is static. Then, when the motor needs to be braked, a reverse control voltage is output, and an armature current value is detected. When the detected armature current value is equal to the static armature current value, the braking control action of the direct current brushed motor is completed. The invention can complete the purpose of braking and stopping the direct current brush motor in a short time under any state, and can be applied to different direct current brush motors to obtain the same effect.

Description

Brake control method and system for DC brushed motor without Hall component

technical field

The present invention relates to a braking method and system for a DC brushed motor (Direct Current Brushed Motor), in particular to a braking control method and system for a DC brushed motor without a Hall Sensor.

Background technique

In general DC brushless motor (Brushless Motor) control systems, most of them are equipped with Hall components, so the speed FG (Frequency Generator) signal can be obtained directly, or the speed signal can be generated through an external chip by using three-phase control signals. And when the speed signal is zero, it means that the motor completes the braking and enters the stop state.

In addition, many DC brushed motors also contain Hall components for better control performance and easy access to feedback (Feedback) signals. However, in the consumer market where the price is getting lower and lower, this kind of motor cannot meet the cost demand, so a DC motor with a simpler structure and no Hall components is needed.

However, using a motor without a Hall element has many problems that did not exist in the past to be solved urgently, one of which is the braking (stopping) problem of the motor.

Generally, there are two methods of electric motor braking: the first one is to immediately stop supplying current to the motor, so that the motor loses power and gradually enters a stop state. However, this method takes a long time, cannot quickly achieve the purpose of complete stop, and cannot meet the use requirements in many occasions. The second is to provide the motor with a reverse current (Reverse Current) to make it have a greater deceleration (Deceleration), so as to quickly complete the braking action. However, in a DC motor system without speed signal feedback, this method is not easy to accurately know whether the motor is in a completely stationary state, especially when the load (Load) is different, it may cause early stop braking or excessive braking. reverse phenomenon.

Please refer to FIG. 1 , which is a circuit block diagram of a brushless DC motor system with Hall components in the prior art. The brushless DC motor system 100 with Hall components in the prior art can directly detect and feed back the motor speed. The processing unit (Processing Unit) 101 drives the brushless DC motor 103 through the motor driver (Driver) 102. After the motor 103 rotates, the motor driver 102 generates a speed signal, which is provided to the processing unit 101 for speed control and braking control. However, the disadvantages of this system are higher price and higher circuit complexity.

Patent No. 584836 of Taiwan Province of my country proposes a control device and method for calculating the motor coefficient and rotational speed by detecting the armature current (Armature Current) of a DC motor without a Hall component. This method needs to carry out mathematical operations according to different motors to obtain the motor coefficients, and the program portability is low. In addition, this method uses a differential amplifier circuit (Differential Amplifier circuit) to calculate the armature current, but it cannot ensure the matching between the used resistors and solve the problem of noise interference, so the calculated armature current also has errors. Therefore, using this erroneous armature current to substitute into the formula, the accuracy of the derived motor coefficient and rotational speed is low. Moreover, this patent is used to calculate the motor coefficient and rotational speed, and does not disclose how to perform brake control.

Contents of the invention

In view of the above-mentioned defects, the technical problem to be solved by the present invention is to provide a brake control method for a DC brushed motor without Hall components.

In order to achieve the above object, the DC brushed motor brake control method without Hall components of the present invention includes:

1) After pre-braking the brushed DC motor without Hall components, detect the armature current value of the brushed DC motor as the static armature current value; and

2) When a brake command is received, perform the brake action of the motor, and at the same time detect the armature current value of the motor until it is equal to the static armature current value.

Wherein said step 1) comprises:

11) Detect the armature current value of the DC brushed motor;

12) Generate a periodically changing brake control signal according to the detected armature current value, and detect the armature current value of the motor when the brake control signal is in a low level state; and

13) If the armature current values measured continuously for a predetermined number of times are all the same, stop generating the brake control signal, and record the measured armature current value as the static armature current value.

Preferably, the low-level state of the brake control signal in step 12) is a no-voltage state.

Preferably, the low level state of the brake control signal in step 12) is zero voltage.

Preferably, the step 12) further includes changing the voltage of the braking control signal according to each change in the difference between the measured armature current values.

In the DC brushed motor brake control method without Hall components, the step 2) includes:

21) Generate a periodically changing braking control signal;

22) During the low level period of the brake control signal, detect the armature current value of the motor, and record it as detecting the armature current value; and

23) Comparing the detected armature current value of the motor with the static armature current value, if the detected armature current value is equal to the static armature current value, stop generating the braking control signal.

Preferably, the step 21) further includes: changing the voltage of the braking control signal according to each change in the difference between the measured armature current values.

The present invention also provides a DC brushed motor braking control system without Hall components, including:

The processing unit generates a periodically changing braking control signal according to the braking command;

The motor driver receives the periodically changing brake control signal and generates a motor drive signal;

A DC brushed motor is driven by a driving signal of the motor;

A current detection device, which detects the armature current value of the DC brushed motor during the low level period of the brake control signal, and outputs the detected armature current value to the processing unit;

Wherein, the processing unit stops generating the brake control signal when the armature current value is equal to the static armature current value.

Preferably, after receiving the braking command, the processing unit generates the braking control signal with a fixed voltage value or adjusts the voltage value of the braking control signal according to the armature current value measured by the current detection device .

Preferably, the processing unit is a central processing unit.

Compared with the prior art, the beneficial effects of the present invention are:

First of all, the method provided by the present invention judges whether the motor is stalled by detecting the armature current value, and can accurately and quickly control the DC motor to completely brake and stop in a short time. Secondly, the method provided by the present invention can be applied to different DC brushed motors to obtain the same effect, and can avoid the influence caused by component error values of the motors, circuit offsets, and individual differences of the motors. This is because the method detects the static armature current for each motor and obtains the static armature current value of the motor. Using this value for the brakes avoids differences between motors affecting the accuracy of the brakes.

Description of drawings

Fig. 1 is the circuit block diagram of the brushless DC motor system with Hall assembly in the prior art;

Fig. 2 is a flow chart of a braking control method for a DC brushed motor without a Hall component in an embodiment of the present invention;

Fig. 3 is a flowchart of the pre-braking process in Fig. 2;

Fig. 4 is the output waveform of the brake control signal when the pulse wave detection current mode;

Fig. 5 is a flow chart of performing the braking process in Fig. 2;

Fig. 6 is a circuit block diagram of a DC brushed motor brake control system without Hall components in an embodiment of the present invention.

Component label description:

100 Brushless DC Motor System with Hall Components

101 processing unit

102 motor driver

103 DC brushless motor

600 Brake Control System of DC Brushed Motor Without Hall Components

603 DC brushed motor

604 current detection device

Detailed ways

The principle of the present invention is: by detecting the armature current value of the DC brushed motor, to know whether there is a current generated by the back electromotive force (Back Electromotive Force) caused by the rotation of the motor.

In the invention, when the system is started, the motor is braked in advance, and the static armature current value of the motor is detected and recorded when the motor is at rest.

When the motor needs to be braked, the reverse current is used to quickly decelerate the motor, and the armature current value is continuously detected, and the armature current value is compared with the static armature current value. When the armature current value is equal to the static armature current value, it means that the motor is in a static state, stop providing reverse current and complete the braking action.

Since the current value is the same, it means that the counter electromotive force generated by the motor rotation is also the same, so the motor reaches the same speed as the pre-braking (original static state), that is, the speed is zero, and the brake control action of the DC brushed motor is completed.

Please refer to FIG. 2 , which is a flowchart of a braking control method for a brushed DC motor without a Hall component according to the present invention. The method comprises the steps of:

In step S202, after pre-braking the DC brushed motor without Hall components, detect the armature current value of the motor as the static armature current value. This step only needs to be performed once at system startup.

Step S204, check whether a braking command is received, if yes, skip to step S206; if not, repeat this step.

Step S206, perform the braking action of the motor, and detect the armature current value of the motor at the same time, until the armature current value of the motor is equal to the static armature current value described in step S202.

FIG. 3 is a flowchart of the pre-braking process in FIG. 2 . The steps of the pre-braking process will be described below based on this figure.

Step S302, detecting the armature current value of the motor.

Step S304, generating a periodic braking control signal with a reverse voltage according to the armature current value detected in step S302, so as to make the DC brushed motor decelerate.

Step S306, detecting the armature current. When the brake control signal is low voltage, the armature current value is detected. This is the pulse width detection current method, which will be described later. The low voltage of the brake control signal refers to a state in which the voltage of the brake control signal is 0 or has no voltage.

Step S308 , checking whether the armature current values measured in consecutive pulse width periods of a predetermined number N (N is a positive integer) are the same. If yes, skip to step S310. If not, return to step S306.

Step S310, stop generating the braking control signal, and record the measured armature current value as the static armature current value.

The present invention detects the armature current value of the motor by using the pulse width detection current during the pre-braking deceleration process. The pulse width detection current method will be described in detail below.

FIG. 4 is an output waveform of the brake control signal in the pulse width detection current mode. As shown in the figure, the braking control signal is a periodic pulse width signal. In each pulse width period, the control voltage is output for a part of the time, such as the first and second control voltages (ie, reverse voltage or high voltage) in Figure 4, and the control voltage is not output for the rest of the time (ie, brake control voltage). The signal is a low voltage, and the brake signal is a low voltage including no voltage state or a voltage of 0). When the control voltage is not output, the current of the motor is completely generated by the back electromotive force of the motor, and current detection can be carried out at this time. Starting from the kth (k is a positive integer) detected current value, if the measured armature current values are the same in the preset number of consecutive pulse width periods N, it means that the DC motor has not been detected for a long enough time. Therefore, it can be determined that the motor speed is 0. During the current detection process, the control voltage can be changed according to the amount of difference between the measured armature current values each time. For example, when the difference between the detected current values is relatively large, a relatively large motor control voltage (such as the first control voltage) can be provided. And the smaller the difference between the detected current values, the smaller the motor control voltage (such as the second control voltage) can be provided.

FIG. 5 is a flowchart of the braking process in FIG. 2 .

Step S502, generating a periodic braking control signal with reverse voltage.

Step S504, detecting the armature current value of the motor when the voltage of the braking control signal is 0.

Step S506, judging whether the measured armature current value is equal to the static armature current value. If yes, go to step S508; if not, go back to step S504.

In step S508, the electric motor is in a static state, and the brake control signal is stopped.

Because in each pulse width detection current of the brake control signal, there is voltage in a part of the pulse width time, and the voltage is 0 in the rest of the time, so that the detected armature current value is the quiescent armature current in the original completely quiescent state value, and the sum of the current value formed by the counter electromotive force generated by the rotation of the DC motor. When the detected armature current value is the same as the static armature current value in the original completely static state, it means that the counter electromotive force generated by the motor is zero and the motor is in a static state.

It should be noted that no matter in the pre-braking process or the braking process, if the control voltage is continuously supplied to the motor without detecting the armature current, it may cause the reverse rotation of the motor. Since the present invention utilizes the characteristic that the speed of the circuit is much faster than the mechanical reaction speed of the motor, and closely monitors the armature current of the motor during the pre-braking process or the execution of the braking process, all braking processes can be precisely controlled.

Fig. 6 is a circuit block diagram of the braking control system of the DC brushed motor without Hall components of the present invention. The system 600 includes a processing unit 101 , a motor driver 102 , a DC brushed motor 603 and a current detection device 604 . The processing unit 101 generates a periodic brake control signal with a reverse voltage according to the brake command. The motor driver 102 generates a motor driving signal to drive the DC brushed motor 603 after receiving the braking control signal. The current detection device 604 detects the armature current value of the motor during the low level (ie no voltage state or voltage is 0) time of each pulse width period, and outputs the measured armature current value to the processing unit 101 .

In addition, the processing unit 101 also adjusts the voltage value of the braking control signal according to the armature current value measured by the current detection device 604 after receiving the pre-braking command or the braking command. For example, when the difference between the current detection values is relatively large, a brake control signal with a relatively high voltage may be provided. When the difference between the detected current values becomes smaller, a brake control signal with a lower voltage can be provided.

Wherein, the processing unit 101 can be implemented by a common central processing unit, and the current detection device 604 can be implemented by a resistor and an operational amplifier circuit.

The present invention can be applied to different DC brushed motors and has the same effect, and can avoid the influence caused by component error values on the circuit, circuit offset and individual differences of the motors.

The above is only a preferred embodiment of the present invention, it should be pointed out that, for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (10)

1, a kind of brake control method of DC electromotor with brush that does not have Hall subassembly is characterized by, and comprises step:

1) after the DC electromotor with brush that will not have a Hall subassembly braked in advance, the armature current value that detects this DC electromotor with brush was as the stationary armature current value; And

2) when receiving braking commands, carry out the brake of this motor, and detect the armature current value of this motor simultaneously, equal described stationary armature current value up to it.

2, the brake control method of DC electromotor with brush of no Hall subassembly according to claim 1 is characterized by, and wherein said step 1) comprises:

11) detect the armature current value of this DC electromotor with brush;

12) according to the armature current value of above-mentioned detection, produce periodically variable brake control signal, and when this brake control signal is in low level state and make the armature supply of motor be produced by the back electromotive force of motor fully, detect the armature current value of this motor; And

13) if continuous measurement reaches the armature current value of pre-determined number when all identical, then stop to produce described brake control signal, and measured armature current value is recorded as described stationary armature current value.

3, the brake control method of DC electromotor with brush of no Hall subassembly according to claim 2 is characterized by, and the low level state of the brake control signal of described step 12) is a no-voltage condition.

4, the brake control method of DC electromotor with brush of no Hall subassembly according to claim 2 is characterized by, and the low level state of the brake control signal of described step 12) is that voltage is 0.

5, the brake control method of DC electromotor with brush of no Hall subassembly according to claim 2 is characterized by, and described step 12) also comprises: according to the variation of the gap amount of the armature current value that records at every turn, change the voltage of brake control signal.

6, the brake control method of DC electromotor with brush of no Hall subassembly according to claim 1 is characterized by, described step 2) comprising:

21) brake control signal of generation one-period property variation;

22) at the low level state of described brake control signal and when making the armature supply of motor produce by the back electromotive force of motor fully, detect the armature current value of described motor, be recorded as the detection armature current value; And

23) the detection armature current value of more described motor and described stationary armature current value if described detection armature current value equals described stationary armature current value, then stop to produce described brake control signal.

7, the brake control method of DC electromotor with brush of no Hall subassembly according to claim 6 is characterized by, described step 21) also comprise: according to the variation of the gap amount of the armature current value that records at every turn, change the voltage of brake control signal.

8, a kind of DC electromotor with brush brake control system that does not have Hall subassembly comprises:

Processing unit according to braking commands, produces periodically variable brake control signal;

Motor driver receives described periodically variable brake control signal, produces motor drive signal;

DC electromotor with brush receives the driving of this motor drive signal;

It is characterized by, further comprise:

Current sensing means detects the armature current value of this DC electromotor with brush between the low period of this brake control signal, and exports detected armature current value to described processing unit;

Wherein, when described processing unit equals described stationary armature current value at described armature current value, then stop to produce described brake control signal.

9, the DC electromotor with brush brake control system of no Hall subassembly according to claim 8, it is characterized by, described processing unit is adjusted the magnitude of voltage of described brake control signal according to the measured armature current value of described current sensing means after receiving described braking commands.

10, the DC electromotor with brush brake control system of no Hall subassembly according to claim 8 is characterized by, and described processing unit is a central processing unit.

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