Servo motor and harmonic drive selection?

[kuv]

How can i sure i have select the right choice of this two combination?

If i require an output torque of 200Nm, which one should i choice when 2 choices have been given
1. a 4Nm output torque servo motor with 50 ratio
harmonic drive
or
2. a 2Nm output torque servo motor with 100 ratio
harmonic drive

Can anyone please explain and help me to figure it out?

 

[Barry1961]

You would need to post much more information about your application to find out.

What is the required output rpm?
What type of load is it driving?
What is move profile and duty cycle?
What type of servo motor?

Barry1961

 

[kuv]

The driving system is applied for robot arm. The output rpm and torque are required 160 degree/second and 200Nm. The servo motor is a dc brushless type.

 

[israelkk]

Harmonic drive gears at those ratios has a quite low efficiency. Therefore, neither one of the solutions will do the job. You will need more than 2Nm or 4Nm fro the motor/s with 50 or 100 ratio Harmonic gears drives to compensate for the lower efficiency.

However, this is not enough, you need more torque for the acceleration of the arm inertia. Adding to all of this you need to do the servo system control analysis and type of control (PI, PID etc.) including stability, sensitivity, speed and position accuracy, etc. Only this analysis will reveal what is the best/optimum gear ratio.

 

[Barry1961]

With the very limited information given I would use the 100:1 reduction.

With a peak output rpm of 27 the peak motor speed would be 2700 rpm. This in my experience is in a good speed range for a servo motor with gearbox. The 100:1 should keep the reflected inertia ratio below 10:1 for crisp response and the rpm is low enough that the drive should be fairly quiet.

Since this is a fairly small drive the motor and gearbox are probably rated for 4000+ rpm but I have never really like running over 3000 rpm without a good reason.

Is your torque requirement peak? Load at max acceleration or E-Stop?

Barry1961