Q: Ease-in ease-out ramp Micro Maestro, "Giant servo"

Support Servo controllers and servos
1

Hi all,
I’ve got a couple of Micro Maestro servo controllers on the way, and general phone support thought they would suit my needs, but I thought I would ask if there were any details I’ve overlooked on the forum here.

The application is basically a giant animatronic flower. I’m using Roboteq motor controllers and an Arduino Mega. The motors on the AZ rotation is 80A, there are 2 1000lb linear actuators and a smaller 9A motor. Basically I am driving a 2 ton servo. All actuators are fed back with a 10K pot.

The AZ movement is what I am most concerned about. The Roboteq controller does not handle ramp up, and more importantly ramp down, well for a “servo” that weighs over a ton and takes 20-30 seconds to move 60 degrees. It can move scary fast, but because of the mass involved and the danger to bystanders we have to slow it to a crawl. The flower is basically a 400 lb weight on the end of a 25 foot arm. F=ma, the ramping down “ease-out” is going to be really important here!

Is the Micro Maestro going to be the trick? From what I have read I will send it a position via the serial port, and it will determine the easing and send that via a simulated r/c reciever output to the motor controller. The pots go to the motor controller and I read the position for whatever purpose I like via the rs-232 output on the motor controller.

We have tried rs-232 to the motor controller, in R/C mode we have been able to get better control of the important AZ rotation.

Sound correct? Ideas?

2

Ah, in better reading the manual I see I can connects the pots to the Micro Maestro, and maybe free-run the motor controller like a giant H bridge…

3

Hello,

I am scared to hear that you are connecting this to something that could present danger to bystanders! I hope that you will set up your system so that the speed is limited by both the Maestro and your motor controller independently, so that a failure of any one piece would not cause any danger. One thing to consider is that if noise on the reset line causes the Maestro to reset, then depending on your configuration, the output might instantly go to a different position and cause some damage. So you should probably have the channel initially be off, and be very careful about starting it up after an error or reset.

At the lowest acceleration setting, with no speed limit, the Maestro takes about a second to accelerate and a second to decelerate as it moves across the 1-2ms range. Is that going to be slow enough for you?

-Paul

4

We’ll see if 1 second does it and I will let you know. The controllers should be here tomorrow and I will run them asap. I have the motor controllers set to the lowest setting and it is slow and smooth. It looks like the Micro will only be able to support 3 “servos” with analog “pot” input, I may have to get the larger ones for the two flowers since there are 8 motors. I’ll test one unit with the micro in any case!