Basic Motor Position Control Application

In this application, you will learn how to control a DC motor’s exact position in degrees using the Position Mode of the SMD Red module. You will enter a target angle between 0 and 360, and the motor will rotate precisely to that point using encoder feedback.

About Tools and Materials:

SMD Red (Purchase Here)

SMD USB Gateway (Purchase Here)

Arduino Gateway Module (Purchase Here)

BDC Motor (Purchase Here)

Step 1: Hardware & Software Overview

Project Key Components

SMD Red: Controls the brushed DC motor and reads encoder feedback for accurate position control.
BDC Motor: Converts electrical energy to mechanical rotation and provides position feedback via encoder signals.

Project Key Features

Precise angle-based control: Move the motor shaft to an exact angle between 0° and 360°.
Real-time encoder feedback: Monitor actual shaft position with high-resolution encoder data.
Tunable PID position control: Customize responsiveness and stability using: set_control_parameters_position
Encoder-integrated control loop: Closed-loop control ensures accurate positioning over time.

Step 2: Assemble

Getting Started

Hardware Setup

Connect the SMD to the PC or Arduino board using USB Gateway Module or Arduino Gateway Module.
Connect the 100 RPM BDC Motor with Encoder to the motor ports of the SMD Red.
Make sure that the SMD is powered and all connections are correct.

Project Wiring Diagram

Step 3: Run & Test

Run the Script

After launching the script, you will be prompted to enter a desired angle between 0 and 360 degrees. The motor will rotate to the target position using encoder feedback and stop.

Codes

from smd.red import *  # Import SMD Red control library
from serial.tools.list_ports import comports  # For listing available serial ports
from platform import system  # To detect the operating system
import time  # For sleep/delay
import math  # For mathematical operations

# Automatically detect and return the correct USB port connected to SMD Red
def USB_Port():
    ports = list(comports())
    usb_names = {
        "Windows": ["USB Serial Port"],
        "Linux": ["/dev/ttyUSB"],
        "Darwin": ["/dev/cu."]  # macOS ports usually start with /dev/cu.
    }
    os_name = system()
    for port, desc, _ in ports:
        if any(name in port or name in desc for name in usb_names.get(os_name, [])):
            return port
    return None

def main():
    port = USB_Port()
    if not port:
        print("No port found.")  # If no port is found, exit the program
        return

    master = Master(port)  # Create a Master object to control SMD Red
    motor_id = 1  # ID of the connected motor
    CPR = 6533  # Encoder Counts Per Revolution

    # Attach the motor and configure its basic parameters
    master.attach(Red(motor_id))
    master.set_shaft_cpr(motor_id, CPR)  # Set encoder resolution
    master.set_shaft_rpm(motor_id, 100)  # Set nominal RPM
    master.set_control_parameters_position(motor_id, 0.5, 0.0, 20.0)  # Set PID gains for position control
    master.set_operation_mode(motor_id, OperationMode.Position)  # Enable position control mode
    master.enable_torque(motor_id, True)  # Enable torque so the motor can move

    while True:
        try:
            # Get target angle from user input and keep it in [0, 360) range
            angle = float(input("Enter target angle (0-360°): ")) % 360

            # Convert angle in degrees to encoder counts
            target = angle * (CPR / 360)

            # Send position command to the motor
            master.set_position(motor_id, target)

            # Wait for movement to complete
            time.sleep(0.5)

            # Read actual encoder position
            current = master.get_position(motor_id)

            # Convert encoder counts back to degrees
            actual = current * (360 / CPR)

            # Print both target and actual angles
            print(f"Target: {angle:.2f}°, Actual: {actual:.2f}°\n")

        except KeyboardInterrupt:
            # On user interrupt (Ctrl+C), disable torque and stop the motor
            master.enable_torque(motor_id, False)
            break

# Entry point of the script
if __name__ == "__main__":
    main()

#include <Acrome-SMD.h>
#define BAUDRATE 115200         // Serial communication speed
#define CPR 6533                // Counts per revolution of the encoder
#define ID 1                    // ID of the SMD Red module

Red master(ID, Serial, BAUDRATE);  // Create SMD Red object

void setup() {
  Serial.begin(115200);             // Start serial monitor
  master.begin();                   // Initialize communication with SMD Red
  master.torqueEnable(1);          // Enable motor torque
  master.setOperationMode(PositionControl);  // Set operation mode to Position Control
}

void loop() {
  // Read joystick X and Y values from module 1
  int joystickX = master.getJoystickX(1);
  int joystickY = master.getJoystickY(1);

  // If joystick is moved beyond dead zone
  if (abs(joystickX) > 10 || abs(joystickY) > 10) {
    // Calculate angle based on joystick direction
    float angle = atan2(joystickY / 100.0, joystickX / 100.0);
    float angleDegrees = fmod(degrees(angle) + 360.0, 360.0);  // Normalize angle to 0–360°
    
    // Convert angle in degrees to encoder position (CPR)
    int position = angleDegrees * (CPR / 360.0);

    master.setpoint(1, position);  // Send position command to motor

    // Debug output
    Serial.print("Target Angle: "); Serial.println(angleDegrees);
    Serial.print("Target CPR: "); Serial.println(position);
  }

  delay(100);  // Small delay for stability
}

PreviousBasic Motor Control Application Using PWM Input NextBasic Motor Torque Control Application

Last updated 7 months ago

from smd.red import * # Import SMD Red control library from serial.tools.list_ports import comports # For listing available serial ports from platform import system # To detect the operating system import time # For sleep/delay import math # For mathematical operations # Automatically detect and return the correct USB port connected to SMD Red def USB_Port(): ports = list(comports()) usb_names = { "Windows": ["USB Serial Port"], "Linux": ["/dev/ttyUSB"], "Darwin": ["/dev/cu."] # macOS ports usually start with /dev/cu. } os_name = system() for port, desc, _ in ports: if any(name in port or name in desc for name in usb_names.get(os_name, [])): return port return None def main(): port = USB_Port() if not port: print("No port found.") # If no port is found, exit the program return master = Master(port) # Create a Master object to control SMD Red motor_id = 1 # ID of the connected motor CPR = 6533 # Encoder Counts Per Revolution # Attach the motor and configure its basic parameters master.attach(Red(motor_id)) master.set_shaft_cpr(motor_id, CPR) # Set encoder resolution master.set_shaft_rpm(motor_id, 100) # Set nominal RPM master.set_control_parameters_position(motor_id, 0.5, 0.0, 20.0) # Set PID gains for position control master.set_operation_mode(motor_id, OperationMode.Position) # Enable position control mode master.enable_torque(motor_id, True) # Enable torque so the motor can move while True: try: # Get target angle from user input and keep it in [0, 360) range angle = float(input("Enter target angle (0-360°): ")) % 360 # Convert angle in degrees to encoder counts target = angle * (CPR / 360) # Send position command to the motor master.set_position(motor_id, target) # Wait for movement to complete time.sleep(0.5) # Read actual encoder position current = master.get_position(motor_id) # Convert encoder counts back to degrees actual = current * (360 / CPR) # Print both target and actual angles print(f"Target: {angle:.2f}°, Actual: {actual:.2f}°\n") except KeyboardInterrupt: # On user interrupt (Ctrl+C), disable torque and stop the motor master.enable_torque(motor_id, False) break # Entry point of the script if __name__ == "__main__": main()