Angle sensor working principle and application introduction

Angle displacement sensor is an electronic component that uses angle changes to locate the position of an object. It is suitable for servo systems of automobiles, engineering machinery, space devices, missiles, aircraft radar antennas, as well as injection molding machines, woodworking machinery, printing machines, electronic rulers, robots, engineering monitoring, computer-controlled sports equipment and other occasions that require accurate displacement measurement. This article introduces the principle of angle displacement sensor and its application examples.

Principle of Angle Displacement Sensor

Angle Sensor This is used to detect angles. It has a hole in its body that fits the Lego axle. When attached to the RCX, the angle sensor counts once for every 1/16 turn of the axle. The count increases when turning in one direction and decreases when the direction of rotation changes. The count is related to the initial position of the angle sensor. When the angle sensor is initialized, its count value is set to 0, and you can reset it programmatically if necessary.

Angular displacement sensor example

If you connect the angle sensor to any of the drive shafts between the motor and the wheel, you must factor the correct gear ratio into the data you read. Here's an example of a calculation. On your robot, the motor is connected to the main wheel with a 3:1 gear ratio. The angle sensor is connected directly to the motor. So its gear ratio to the drive wheel is also 3:1. That is, for every three revolutions of the angle sensor, the drive wheel rotates once. Each revolution of the angle sensor counts 16 units, so 16*3=48 increments equal one revolution of the drive wheel. Now, we need to know the circumference of the gear to calculate the distance traveled. Fortunately, each LEGO gear has its diameter marked on the tire. We chose the largest wheel with an axle, which has a diameter of 81.6CM (LEGO uses metric units), so its circumference is 81.6×π=81.6×3.14≈256.22CM. Now we have all the known quantities: the distance the gear travels is 48 divided by the increments recorded by the angle and then multiplied by 256. Let's summarize. R is called the resolution of the angle sensor (count value per rotation), G is the transmission ratio between the angle sensor and the gear. We define I as the increment of the angle sensor per rotation of the wheel. That is:

I = G × R

In this example, G is 3, and for the Lego Angle Sensor, R is always 16. Therefore, we can get:

I = 3 × 16 = 48

The distance the gear travels per rotation is exactly its circumference C, and applying this equation, using its diameter, you can come to this conclusion.

C=D×π

In our example:

C = 81.6 × 3.14 = 256.22

The final step is to convert the data recorded by the sensor - S - into the distance the wheel traveled - T, using the following equation:

T=S×C/I

If the photoelectric sensor reads a value of 296, you can calculate the corresponding distance:

T=296×256.22/48=1580 The unit of distance (T) is the same as the unit of wheel diameter.

Angle displacement sensor is actually used

Using an angle sensor to control your wheels can indirectly detect obstacles. The principle is very simple: if the motor angle sensor structure is running, but the gear does not turn, it means that your machine has been blocked by an obstacle. This technology is very simple to use and very effective; the only requirement is that the moving wheel cannot slip on the floor (or slip too many times), otherwise you will not be able to detect the obstacle. This problem can be avoided if an idle gear is connected to the motor. This wheel is not driven by the motor but by the movement of the device: during the rotation of the driving wheel, if the idler wheel stops, it means that you have hit an obstacle.

Angle sensors are very useful in many situations: controlling the position of arms, heads and other movable parts. It is worth noting that when running too slowly or too fast, the RCX will suffer in terms of accurate detection and counting. In fact, the problem is not with the RCX, but its operating system. If the speed exceeds its specified range, the RCX will lose some data. Steve Baker has experimentally proved that the speed range between 50 and 300 revolutions per minute is a more appropriate range, within which there will be no data loss problem. However, in the range below 12rpm or above 1400rm, some data will be lost. In the range of 12rpm to 50rpm or 300rpm to 1400rpm, RCX will occasionally have data loss problems.