Speed control refers to control the speed of the machine through the speed reference. Through internal digital setting, analog voltage or communication, the servo drive could achieve fast and precise control of the mechanical speed. Therefore, the speed control mode is mainly used to control the rotation speed, or use the host controller to realize the position control, and the host controller output is used as the speed reference, such as analog engraving and milling machine.

The speed control block diagram is as follows:

                                                                                          Figure1 speed control diagram

Set the parameter P0-1 to 2 through the panel or debugging tool on PC to make the servo drive work in speed control mode.

Relevant function code:

Speed Reference Input Setting

Speed Reference Source

There are two sources of speed reference in speed control mode, which could be set by [P1-1].

Relevant function code:

Internal speed reference

Set the speed value through the function code [P1-2] as the speed reference.

Relevant function codes:

Analog voltage input as a reference

Take the analog voltage signal output by the host controller or other equipments, processed as a speed reference.

Analog voltage setting method:

Figure 2 flowchart of setting speed reference by analog voltage

Glossary:

Zero drift: Value of the servo drive sampling voltage relative to GND when the input

voltage of the analog channel is zero.

Offset: Input voltage value of the analog channel when the sampling voltage is zero after

zero drift correction.

Dead zone: Input voltage range of the analog channel when the sampling voltage is zero.

                                                               Figure 3 Analog signal after-offset

After completing the correct settings, you could view the input voltage values of AI_1 and AI_2 through U0-21 and U0-22

Relevant function codes:

Acceleration and deceleration time setting

The acceleration/deceleration time setting refers to convert a speed command with a relatively high acceleration into a speed command with a relatively gentle acceleration, so as to achieve the purpose of controlling the acceleration.

In the speed control mode, excessive acceleration of the speed command would cause the vibration. At this time, increase the acceleration or deceleration time to achieve a smooth speed change of the motor and avoid mechanical damage caused by the above situation.

                                     Figure 4 diagram of acc. and dec. time

Actual acceleration time T1 = speed reference / 1000 * acceleration time

Actual deceleration time T2 = speed reference / 1000 * deceleration time

Relevant function codes:

Speed Reference Limitation

The servo drive could display the value of the speed reference in speed mode.

Sources of speed instruction limits include:

[P1-10]: Set the maximum speed limit value

[P1-12]: Set forward speed limit value

[P1-13]: Set the reverse speed limit value

Maximum motor speed: determined according to the model of the motor

| The amplitude of the forward speed reference | ≤ min {Max. motor speed, P1-10, P1-12}

| The amplitude of the negative speed reference | ≤ min {Max. speed of the motor, P1-10, P1-13}

Relevant function codes:

6.3.4 Zero Speed Clamp Function

Zero speed clamping function means that when the zero speed clamping signal (ZCLAMP) is valid, when the absolute value of the speed reference is lower than the zero speed clamping speed value, the servo motor is in the locked state. At this time, the servo drive is in position lock mode, and the speed reference is invalid.

Relevant function codes:

Figure 5 Zero Speed Clamp waveform

Speed-relevant DO Signals

Different DO signals are output to the host controller based on comparison between the speed feedback after filter and different thresholds. We need to assign different function for the DO terminals and set the valid logic.

Motor Rotation DO Signal

After the speed reference is filtered, the absolute value of the actual speed of the servo motor reaches [P5-16] (rotation detection speed threshold), then the motor is considered to be rotating. At this time, the DO terminal of the servo drive could output a rotation detection signal. Conversely, when the actual rotation speed of the servo motor does not reach [P5-16], it is considered that the motor is not rotating.

Figure 6-14 motor rotation DO signal

Relevant function codes:

Zero speed signal

The absolute value of the actual speed of the servo motor is less than a certain threshold [P5-19], it is considered that the servo motor stops rotating, and the DO terminal of the servo drive could output a zero speed signal at this time. Conversely, if the absolute value of the actual speed of the servo motor is not less than this value, it is considered that the motor is not at a standstill and the zero speed signal is invalid.

Figure 6 zero speed signal waveform

Relevant function codes:

Speed Consistent DO Signal

In speed control, when the absolute value of the difference between the motor speed after filter and the speed reference satisfies the setting of [P5-17], the actual motor speed is considered to reach the speed reference. At this moment, the servo drive outputs the speed consistent signal. When the absolute value of the difference between the motor speed after filter and the speed reference exceeds the setting of [P5-17], the speed consistent signal is inactive.

Figure 7 Speed Consistent Waveform

Relevant function codes:

Speed Reached DO Signal

When the absolute value of the motor speed after filter exceeds the setting of[P4-16],the motor speed is considered to reach the desired value. At this moment, the servo drive outputs the speed reached signal. When the absolute value of the motor speed after filter is smaller than or equal to the setting of[P4-16], the speed reached signal is inactive.

Figure 6-17 Speed reached signal waveform

Relevant function codes: