B&R Integrates Torque Determination Into Servo Drives

January 21, 2022 by Shawn Dietrich

Safety is necessary for servo motor applications. How is B&R integrating more safety functions into its newest servo drive?

B&R Servo Drive

B&R supplies and manufactures automation components and controllers. Their ACOPOS servo drive family can provide motion to single compact servo motors up to their linear servo conveyors.


The ACOPOS P3. Image used courtesy of B&R Industrial Automation


The company also provides automation software and hardware to control these servos within an automated machine. The new ACOPOS P3 is now equipped with safe torque determination.


Safe Servo Torque Determination

Servo motors are becoming more popular in automated machinery. As they become more popular, safety technology is not far to follow.

Servo motors can apply a great deal of torque, sometimes enough torque to damage neighboring equipment or people during the setup and tuning phases. Typically, to provide safe functions with a servo motor system, the designer would need to purchase separate safety-rated components, like a safe torque sensor or safe encoder.


The B&R ACOPOS servo drives without housing. Image used courtesy of B&R Industrial Automation [PDF]


While these components are useful, they are also very expensive and take up real estate along the drive train of the motor design. B&R has developed a solution without the need for external sensors. The ACOPOS P3 uses an internal current measurement to determine the motor’s torque. When the torque and motor speed are known, specific safety functions can be applied.


Safe Servo Functions

Safety limited torque (SLT) limits the mechanical torque that the servo can apply. Normally, this can be limited within the parameters of the servo. But, by adding it to the safety side of the servo drive system, we prevent accidental or malicious parameter changes. Limiting the torque of the motor’s mechanical designs can be more conservative and save the project money.


The servo has SLT, SSO, and SBT integrated for safety. Image used courtesy of B&R Industrial Automation


A safe speed observer (SSO) limits the speed that the servo can travel. During the machine’s setup phase or during the machine maintenance, servos need to be moved while the staff is near, on, or inside a machine. This poses a safety risk if tooling is going to be moving at high speed and torque.

With an SSO function, the speed of the servo can be monitored, limited, and stopped so that a user cannot move the servo too fast, allowing an operator to react if something goes wrong or stop the servo entirely.

A safe brake test (SBT) ensures the servo’s holding brake is in good working condition. This function is typically a standard with industrial robots and is required to be run at specific intervals to ensure the brake is not wearing down too quickly.

This function comes in handy when using a servo motor on a linear actuator to suspend a load. If the brake is wearing and may not be able to support the load, the SBT function can stop the operation and alert maintenance staff to perform maintenance on the servo motor.

B&R’s servo with safe torque determination has all three of these functions integrated. These integrations make it a safer servo to use in industrial applications, like running a conveyor.