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VM_102769374-Participant
4-Participant
October 17, 2022
Question

Torque Motor vs Servo Motor

  • October 17, 2022
  • 2 replies
  • 3639 views

Hello Everyone,

In a mechanism (no resistive forces other loads), if I provide a servo motor to a rotating link, it behaves as expected where very minimal forces are generated in links and I believe servo motor just gives enough power/velocity to cause motion. So If i put a measure for reaction forces at various links, the force values are very less.

 

However, If i replace the servo with a finite value torque motor, reaction forces (equivalent in the order of a static case) are generated in the links even when there are no other resistive forces. 

 

I would be much obliged if anyone could explain the above.

 

Thanks in advance

2 replies

M
MartinHanak24-Ruby III
24-Ruby III
October 18, 2022

Hi,

please ask the same question to PTC Support, too.

V
VM_102769374-ParticipantAuthor
4-Participant
October 18, 2022

Hello @MartinHanak , yes, I have mailed the customer support. 

V
VM_102769374-ParticipantAuthor
4-Participant
October 18, 2022

Here is a sample mechanism. In a friction less model, the measures of connection reactions at A & B are different when we use a torque motor at center of wheel vs servo motor (angular velocity input). Rx A and Rx B for servo are negligible values as the servo does bare minimum to move the links. But the reactions when run with torque motor are much higher and cannot be ignored. So what is causing this resistance and generation of forces at connections?

VM_10276937_0-1666083935582.png

 

kdirth
21-Topaz I
kdirth21-Topaz I
21-Topaz I
October 18, 2022

A servo motor will provide a constant angular speed (deg/sec) with a varying load.  In your example, the flywheel will turn at a constant angular velocity.

 

A torque motor will provide a constant torque (kg m).  In your example, the fly wheel will accelerate and decelerate based on the kinetic load of the system.

There is always more to learn.
    kdirth
    21-Topaz I
    kdirth21-Topaz I
    21-Topaz I
    October 26, 2022

    Newton' 1st and 2nd laws of motion.

     

    As the fly wheel turns, link pushes and pulls on the slider. The slider will oscillate, accelerating and decelerating.  The mass of the link is also accelerating and decelerating as the flywheel turns.

     

    With a servo motor, the speed of the flywheel is constant.  With the torque motor, the torque of the motor is constant.  The speed of the system with a torque motor is determined by when the when energy needed to accelerate the components equals the energy provided by the motor.  I would guess that your servo motor may provide a speed of 100 rpm while the torque motor system balances out at 2500 rpm. making the forces much higher with a torque motor.

    There is always more to learn.
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