Angle sensor working principle and application examples - Solutions - Huaqiang Electronic Network

Angular displacement sensors are essential electronic components used to measure rotational movement and position. These devices find applications in various fields such as automotive systems, engineering machinery, aerospace technology, missile guidance, aircraft radar systems, injection molding machines, woodworking equipment, printing machines, electronic rulers, robotics, structural monitoring, and computer-controlled sports equipment. They provide precise measurements where angular displacement needs to be tracked accurately.

Understanding the Principle of Angular Displacement Sensors

An angular displacement sensor works by detecting changes in rotation. It typically features a hole that fits onto a LEGO axle. When connected to an RCX (a programmable brick used in LEGO Mindstorms), the sensor counts each 1/16th of a full rotation. As the axle turns in one direction, the count increases, and when it reverses, the count decreases. The initial position of the sensor is crucial, as it determines the starting point for counting. Upon initialization, the sensor resets its count to zero, and this can be adjusted through programming if needed.

Practical Example of Angular Displacement Sensor Usage

If the angle sensor is attached to a drive shaft between a motor and a wheel, the gear ratio must be considered when interpreting the data. For example, if a robot has a motor connected to a main wheel with a 3:1 gear ratio, and the sensor is directly connected to the motor, then the sensor's rotation is three times that of the wheel. Since the sensor counts 16 units per revolution, this results in 48 units for every full rotation of the wheel. To calculate the distance traveled, we need the wheel’s circumference.

Each LEGO tire has a marked diameter, which helps determine the circumference. Let’s say the largest wheel has a diameter of 81.6 cm. Its circumference would be 81.6 × π ≈ 256.22 cm. Using this information, we can convert the sensor’s readings into actual distance traveled.

The formula to calculate the distance is:

I = G × R

Where:

• I = Number of increments per wheel rotation
• G = Gear ratio between the sensor and the wheel
• R = Resolution of the sensor (counts per revolution)

In our example, G = 3 and R = 16, so I = 3 × 16 = 48.

To find the distance, use:

T = S × C / I

Where:

• S = Sensor reading
• C = Wheel circumference
• I = Increments per wheel rotation

For instance, if the sensor reads 296, the distance traveled would be:

T = 296 × 256.22 / 48 ≈ 1580 cm

Real-World Application of Angular Displacement Sensors

Angular displacement sensors are widely used in robotics and automation to monitor movement. For example, they can help detect obstacles by comparing motor rotation with wheel movement. If the motor is turning but the wheel isn't, it likely means the robot has hit an obstacle. This method is effective, but it requires that the wheels don’t slip excessively. A solution is to use an idler gear that rotates with the robot’s movement—this allows for more accurate detection of blockages.

These sensors are also useful for controlling the position of robotic arms or other moving parts. However, it's important to note that the RCX (used in LEGO Mindstorms) may experience data loss at extreme speeds. According to Steve Baker's experiments, the optimal range for reliable performance is between 50 and 300 RPM. Outside of this range, some data may be lost, especially below 12 RPM or above 1400 RPM. Between 12–50 RPM and 300–1400 RPM, occasional data loss might occur, so careful calibration is recommended.