CN1760776A - Drive unit for digital control pointer type meters in cars, and drive method - Google Patents

Abstract

The invention is related to automotive meters and instruments. PWM modulation method is adopted in the invention to drive step motor of pointer type meters directly. Relevant algorithms solve nonlinear acceleration and retardation in pointer rotation. Thus, software algorithms accomplish functions such as driving and speed controlling etc, which are implemented by hardware drive formerly. The invention reduces cost of instrument, complexity of hardware, and raises generality of system.

Description

Automobile numerical control pointer instrument driving device and driving method thereof

technical field

The invention relates to the field of automatic control, in particular to the drive control of automobile intelligent instruments.

Background technique

At present, most of the implementation methods of numerical control pointer instruments for automobiles are to use special hardware drive circuits to realize the micro-step drive of the stepping motors of the pointer instruments, such as Harbin Institute of Technology Press in "Stepping Motors and Its Drive Control System" A micro-step driving method of a stepping motor is disclosed in , but the cost of this method is relatively high; the hardware circuit is relatively complicated, which is not conducive to system maintenance; the designer's autonomous control for different applications is not high; it may cause some hardware The resources of the driver chip are wasted.

Contents of the invention

In order to overcome the problems of high cost, complex hardware circuit, waste of hardware resources and poor versatility in the existing scheme of numerical control pointer instrument, the utility model designs a new direct drive scheme of numerical control pointer instrument. The complexity of the hardware circuit can be reduced, the generality of the system can be improved, and the cost of the instrument can be effectively reduced at the same time.

The technical solution of the present invention to solve the technical problem is: to design a numerically controlled pointer meter driving device for automobiles, to realize the micro-step working mode of the stepping motor by using the PWM modulation method, and to directly realize the accurate pointer meter for the bidirectional stepping motor. Display control function; use the algorithm processing on the software to realize the driving control of the entire tachometer, and use the corresponding algorithm to solve the nonlinear acceleration and deceleration in the pointer rotation. The instrument includes: a system initialization module, an input pulse sampling module, a data sampling module, a drive parameter calculation module, a PWM output drive module, and a coordination scheduling module among the modules, and is characterized in that the coordination scheduling module realizes the coordination of the above-mentioned modules Scheduling work; the data sampling module collects the physical characteristic parameters of the micro-stepping motor; the input pulse sampling module: performs input pulse sampling; the drive parameter calculation module converts the collected data into the angle of the micro-stepping motor; the PWM drive module generates A specific PWM sequence of pulses executes the drive of the micro stepping motor.

The present invention also designs a method for realizing the direct drive of a numerically controlled pointer instrument for automobiles, which is characterized in that the method includes the following steps: the system initialization module initializes the I/O port of the MCU, the timer, and the interrupt enable; the data sampling module Collect the physical characteristic parameters of the micro-stepping motor; convert the collected data into the angle parameters of the micro-stepping motor; find the corresponding speed in the data list; the PWM drive module receives the driving data and generates a specific PWM sequence pulse; The pulse sequence is output to drive the micro stepping motor to rotate.

The beneficial effects of the invention are: while ensuring the quality of the pointer instrument, achieving high technical index and reliability, it can effectively reduce the cost, reduce the complexity of the hardware circuit and improve the universality of the system.

Description of drawings

Fig. 1 is the overall block diagram of the algorithm of the present invention

Fig. 2 is the flow chart of data acquisition of the present invention

Fig. 3 is the drive parameter calculation flowchart of the present invention

Fig. 4 is the PWM driving flowchart of the present invention

Detailed ways

Below in conjunction with the embodiment of accompanying drawing and numerical control pointer type automobile engine tachometer, the present invention will be further described:

The overall algorithm model frame of the present embodiment is as shown in Figure 1, mainly includes system initialization module (2), data sampling module (3), calculation module (4) of drive parameter, PWM output drive module (5), and each module The coordination scheduling module among them (1). The scheduling module mainly realizes the coordination of the above modules. When the tachometer is just powered on, the coordination module first calls the initialization module, initializes the I/0 port of the MCU, the timer, interrupt enable, etc.; then starts the data acquisition module, Collect the speed data of the engine rotation; after the collection time, call the data calculation module to convert the collected data into the angle of the micro-stepping motor; finally pass the calculation result to the PWM drive module to drive the micro-stepping motor. In order to shorten the time interval between each data sampling, after the PWM driver module receives the driving data, it also starts the data acquisition module at the same time, so that the driving and acquisition can be carried out at the same time, preventing the intermittent phenomenon when the pointer rotates for a period of time , allowing the pointer to achieve a wider speed drive range. In the process of data acquisition, the pulse calculation is mainly realized by means of pulse-triggered interrupt, because the interrupt time is very intermittent and has no obvious impact on the PWM drive.

Figure 2 shows the input pulse sampling function module. The specific sampling method is to use the method of counting the number of pulses at a fixed time to sample the input pulse. In this way, when the input pulse frequency is high, the accuracy of sampling can be guaranteed, and at the same time, a small amount of external interference pulses will not have a great impact on the accuracy of sampling.

Figure 3 shows the drive parameter calculation module, which realizes the calculation of the target position of the pointer. The speed of the engine is converted from the pulse frequency obtained by sampling, and then the target rotation position of the pointer is calculated according to the parameters such as the maximum speed of the engine, the number of teeth, and the maximum rotation angle. The target position of the pointer is compared with the current position, and the rotation angle that the pointer will turn is calculated. The speed of the pointer rotation is proportional to the rotation angle, that is, it is proportional to the change of the engine speed. In the design scheme, the method of looking up the table is used to realize the selection of different speeds, that is, to find out the speed that should be selected according to the different pointer rotation distances. There are certain restrictions on the acceleration during the rotation of the stepper motor. When the acceleration is too large, the rotational torque of the motor will be insufficient, resulting in jitter or even out of step. Therefore, in this project, the acceleration and deceleration process is adopted for the pointer speed change, and the non-linear processing is adopted for this process to avoid out of step, and it also makes the rotation of the pointer more stable and the visual effect is better. After the speed is determined, the corresponding speed change curve table is determined according to the difference between the target speed and the current speed and the distance of rotation. The specific speed change is realized by controlling the frequency change of the PWM pulse duty cycle.

Figure 4 is a functional module that generates dynamic PWM output control pulses to drive the stepper motor to run in microsteps. The principle of stepper motor microstepping drives, knowing that the drive current of the stepper motor is a sinusoidal ladder waveform, the current of this PWM drive waveform The effective value changes in a sinusoidal step, and the electrical signal waveform of the drive shows that the pulse width is close to a sinusoidal curve change. From the perspective of the continuous process of driving, the driving of the stepper motor is to send a certain fixed pulse sequence that is constantly repeated to the stepper motor. The variable modulation process of the fixed pulse sequence is the key part of this design, which determines the important technical indicators such as the smoothness and accuracy of the pointer movement.

Claims (5)

1, a kind of automobile digital control pointer type meters drive unit, comprise: system initialization module, input pulse sampling module, the coordinated scheduling module of data sampling module, driving parameters computing module, PWM output driver module and each intermodule, it is characterized in that the coordinated scheduling module realizes the coordinated scheduling work to above-mentioned each module; Data sampling module is gathered the physical characteristics parameter of micro-step motor; Input pulse sampling module: carry out the input pulse sampling; The driving parameters computing module is gathering the angle that next data-switching becomes micro-step motor to turn over; The PWM driver module produces specific PWM train pulse, carries out the driving of micro-step motor.

2, automobile digital control pointer type meters according to claim 1 is characterized in that, the mode that described data acquisition module interrupts by trigger action realizes step-by-step counting.

3, a kind of automobile is characterized in that with the direct driving method of digital control pointer type meters, said method comprising the steps of: the I/O mouth of system initialization module initialization MCU, and timer interrupts enabling; Data sampling module is gathered the physical characteristics parameter of micro-step motor; The angle parameter that next data-switching becomes micro-step motor to turn over will be gathered; In data list, search corresponding rotating speed; The PWM driver module receives driving data, produces specific PWM train pulse; Output pulse sequence drives micro-step motor and rotates.

4, implementation method according to claim 3 is characterized in that, after the PWM driver module receives driving data, also starts data acquisition module simultaneously.

5, implementation method according to claim 3 is characterized in that, the target location and the current location of pointer compared, and calculates the corner that pointer will turn over and obtains angle parameter, searches the rotating speed that it should be selected according to different pointer rotation distances.

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