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3.1.6 Motion Control

Introduction

In this lesson, we will make a simple motion sensing and controlling device. The MPU6050 is used as a sensor and the stepper motor as a controlled device. With the MPU6050 mounted on the glove, you can control the stepper motor by rotating your wrist.

Components

../_images/list_Motion_Control1.png

Schematic Diagram

T-Board Name

physical

wiringPi

BCM

GPIO18

Pin 12

1

18

GPIO23

Pin 16

4

23

GPIO24

Pin 18

5

24

GPIO25

Pin 22

6

25

SDA1

Pin 3

SCL1

Pin 5
../_images/Schematic_three_one61.png

Experimental Procedures

Step 1: Build the circuit.

../_images/image2511.png

Step 2: Go to the folder of the code.

cd ~/davinci-kit-for-raspberry-pi/c/3.1.6/

Step 3: Compile the code.

gcc 3.1.6_MotionControl.c -lwiringPi -lm

Step 4: Run the executable file.

sudo ./a.out

As the code runs, if the tilt angle of mpu6050 on the Y-axis is larger than 45 ℃, the stepper motor rotates anticlockwise; if less than -45 ℃, the stepper motor rotates clockwise.

Note

If it does not work after running, or there is an error prompt: "wiringPi.h: No such file or directory", please refer to Install and Check the WiringPi.

Code Explanation

double mpu6050(){
    acclX = read_word_2c(0x3B);
    acclY = read_word_2c(0x3D);
    acclZ = read_word_2c(0x3F);
    acclX_scaled = acclX / 16384.0;
    acclY_scaled = acclY / 16384.0;
    acclZ_scaled = acclZ / 16384.0;
    double angle=get_y_rotation(acclX_scaled, acclY_scaled, acclZ_scaled);
    return angle;
}

mpu6050 gets the tilt angle in the direction of the Y-axis.

void rotary(char direction){
    if(direction == 'c'){
        for(int j=0;j<4;j++){
            for(int i=0;i<4;i++)
                {digitalWrite(motorPin[i],0x99>>j & (0x08>>i));}
            delayMicroseconds(stepSpeed);
        }
    }
    else if(direction =='a'){
        for(int j=0;j<4;j++){
            for(int i=0;i<4;i++)
                {digitalWrite(motorPin[i],0x99<<j & (0x80>>i));}
            delayMicroseconds(stepSpeed);
        }
    }
}

If the received direction key is 'c', the stepper motor rotates clockwise; if the key is 'a', the motor rotates anticlockwise. Refer to 1.3.3 Stepper Motor for more details about the calculation of the rotating direction of the stepper motor.

int main()
{
    setup();
    double angle;
    while(1) {
        angle = mpu6050();
        if (angle >=45){rotary('a');}
        else if (angle<=-45){rotary('c');}
    }
    return 0;
}

The tilt angle in the direction of the Y-axis is read from mpu6050, and if it’s larger than 45 ℃, the stepper motor rotates anticlockwise; if less than -45 ℃, the stepper motor rotates clockwise.