Implementing Sensorless Position Control for a DIY Brushless Gimbal Using Arduino and MPU6050

Creating a DIY brushless gimbal with an Arduino and an MPU6050 is a fascinating project! When troubleshooting, if you find that your motor spins in only one direction, there are strategies you can employ to achieve sensorless position control. Sensorless control typically requires precise position feedback, usually provided by sensors like encoders. However, you can still implement a basic control strategy using the electronic speed controller (ESC) and the MPU6050 data combined with your Arduino.

Understanding the Basics of ESC and PID Control

To control a brushless motor in a gimbal application, it’s essential to understand how the electronic speed controller (ESC) works and how to set it up correctly. Ensure that your ESC is capable of handling the motor you're using and that it is configured to spin in both directions. Some ESCs might need calibration procedures to recognize the motor's direction.

Using MPU6050 for Orientation Data

The MPU6050 provides both accelerometer and gyroscope data. By utilizing this data, you can determine the orientation of your gimbal. The gyroscope data gives you the rate of rotation, while the accelerometer data can help with tilt detection.

Implementing a PID Controller

To control the motor, you can implement a PID (Proportional-Integral-Derivative) controller in your Arduino code. This will allow you to adjust the motor speed based on the error between the desired position and the current position, derived from the MPU6050 data.

Reading and Processing Gyro Data

Use the gyro data to determine the current angle of the gimbal. You may need to integrate the gyro readings to obtain the angle over time, but be aware that gyros can drift over time. Therefore, it's important to periodically correct the angle using accelerometer data.

Controlling the ESC with PID Output

Map the output from the PID controller to the PWM signal for the ESC. Ensure that the output range matches the ESC's expected input range, typically 1000 to 2000 microseconds for most ESCs.

Direction Control

Ensure that the motor spins in both directions by checking the wiring and configuring the ESC. Some ESCs have a mode to reverse the motor direction. Also, confirm that the PWM signal changes based on your control logic.

Example Code Snippet

Here’s a simplified example of the structure of your Arduino code:

include Wire.hinclude  mpu;int motorPin  9; // PWM output pin for ESCfloat setpoint  0; // Desired anglefloat input  0; // Current anglefloat output  0; // Motor speed outputfloat Kp  1.0; Ki  0.0; Kd  0.1; // PID constantsfloat previous_error  0;integral  0;void setup() {  (115200);  pinMode(motorPin, OUTPUT);}void loop() {  int16_t ax, ay, az, gx, gy, gz;  (ax, ay, az, gx, gy, gz);  input  gx * 0.000061; // Convert to degrees with example scaling    float error  setpoint - input;  integral   error;  float derivative  error - previous_error;  output  Kp * error   Ki * integral   Kd * derivative;  int escValue  map(output, -255, 255, 1000, 2000);  escValue  constrain(escValue, 1000, 2000);  analogWrite(motorPin, escValue);  previous_error  error;  delay(10); // Loop delay}

Additional Considerations

Calibration: Calibrate the ESC according to the manufacturer's instructions.Noise Filtering: Implement filtering on the gyro data to reduce noise.Power Supply: Ensure that your power supply is adequate for the motor and ESC.Testing: Conduct tests in a safe environment to avoid damage to components or injury.

This approach should allow you to achieve basic control of your brushless gimbal. For more advanced functionality, consider integrating an encoder for more precise position feedback.