The servo motor includes a small DC motor; a set of variable speed gear sets; a feedback adjustable potentiometer; and an electronic control board. Among them, the high-speed rotating DC motor provides the original power to drive the variable speed (reduction) gear set to produce a high torque output. The larger the transmission ratio of the gear set, the greater the output torque of the servo motor, which means that the more powerful it is Bear more weight, but the speed of rotation is also lower

The working principle of micro-line servo motor

A micro servo motor is a typical closed-loop feedback system. The reduction gear set is driven by the motor, and its terminal (output end) drives a linear proportional potentiometer for position detection. The potentiometer converts the corner coordinate into a proportional voltage and feeds it back to the control circuit board. , The control circuit board compares it with the input control pulse signal, generates a correction pulse, and drives the motor to rotate in a forward or reverse direction, so that the output position of the gear set is consistent with the expected value, and the correction pulse tends to 0, so as to achieve The purpose of precise positioning of the servo motor.

How to control a servo motor The standard micro servo motor has three control lines: power, ground and control. The power line and ground line are used to provide the energy required by the internal DC motor and control circuit. The voltage is usually between 4V-6V. The power supply should be isolated from the power supply of the processing system as much as possible (because the servo motor generates noise). Even a small servo motor will pull down the voltage of the amplifier under heavy load, so the power supply ratio of the entire system must be reasonable.

There are three power leads of the servo motor, as shown in the figure. The red line among the three lines of the servo motor is the control line, which is connected to the control chip. The middle is the SERVO working power cord, the general working power is 5V. The third is the ground wire

The movement speed of the servo motor The instantaneous movement speed of the servo motor is determined by the cooperation of the internal DC motor and the variable-speed gear set. Under the constant voltage drive, its value is unique. But its average movement speed can be changed by the control method of segmented pauses. For example, we can subdivide a rotation with a motion amplitude of 90o into 128 stop points, and achieve a 0o—90o change by controlling the length of each stop point. The average speed. For most servo motors, the unit of speed is determined by "degrees/second".

Precautions for using servo motor

Unless you are using a digital servo motor, the above servo motor output arm position is just an inaccurate approximation. Ordinary analog micro servo motor is not a precise positioning device. Even if the micro servo motor products of the same brand and model are used, the difference between them is very big. When the same pulse is driven, different servo motors have a deviation of ±10o. It is also normal. Because of the above reasons, it is not recommended to use pulses less than 1ms and greater than 2ms as drive signals. In fact, the original design table of the servo motor is only in the range of ±45o. Moreover, beyond this range, the linear relationship between the pulse width rotation angles will also become worse. Special attention must be paid to never load a pulse signal that causes the servo motor's output position to exceed ±90o, otherwise it will damage the servo motor's output limit mechanism or gear set and other mechanical components. Since there is no obvious unified standard for the output position angle of the servo motor and the pulse width of the control signal, and the total amount of its stroke is also very different for different manufacturers, the control software must have the function of setting separately according to different servo motors. .