11/8/2022 0 Comments Large servo motor arduino![]() ![]()
The reason I think position control mode is bad however is that as the motor turns, the load is relatively dynamic. I could see that if you are running much lower than this and you have a low-resolution encoder, there isn't enough precision possible in speed control mode. That's why I have to dither between 60 and 61 rpm to get that precise ratio. I am running around 60 rpm but I really need to run around 60.1232342 or whatever rpm. Having said that I agree in terms that the precision in velocity is a problem that's the issue I had (have) with the commercial controllers. What IS important is a precision time base. You really want velocity control, but you want to do it over a long time period (many seconds), so you may have a secondary velocity control loop which takes position measurements over several seconds and uses that to adjust an inner fast velocity loop. In a position control system, the error term is the error between commanded position and actual position, so if you are moving at a constant rate, you have a continuous static error in that loop, which is what you don't want. Velocity is usually the loop outside of the current loop, and position is an integral loop of velocity. So in a servo motor control you usually have three loops - an inner current control loop, an outer velocity loop, and an outer position loop. The difference being that I couldn't find a way to make a DC motor turn slowly enough to handle guide rates using velocity control. I'm not sure that precision telescope tracking is a simple exercise in velocity control but a continuous position update. He was interested in building a native step/dir output controller and was looking for help but I dont have the programming knowledge to do something like that. I went to SiTech once to get my controller repaired. So far it looks like it will work, I have not put it under stars to test it yet. #Large servo motor arduino driver#This feeds the quad A/B input on the servo drives through a 26ls31 line driver and also feeds back to the SiTech to close the look. I ended up going with a SiTech controller that drives some tiny little faulhaber motors that are directly coupled to 2500 line encoders. My telescope mount I have been building uses Mitsubishi brushless servos, they take step/dir, quad A/B, and analog in. I initially tried the OnStep and got Howard to port over to Teensy but it just was not fast enough for the resolution of my scope and I wanted to do satellite tracking if I could. ![]() They will take step/dir input from an external controller. They have the drive built into the motor and are pretty cheap. Two suggestions would be their Gold Twitter (), and Gold Whistle ().Įdited by Coconuts, 01 October 2017 - 07:16 AM. #Large servo motor arduino series#Their Gold series of servo drives are very sophisticated and compact, but will run $500+ in single piece. They also make multi-axis chip sets, and some of these generate +/- 10 volt analog control signals at 16 bit depth, so you can skip designing an output stage and just use an an along servo drive per axis.įor the easiest (but not cheapest) approach to high-end servo control, you could also consider a module from Elmo Motion Control ( ). You do need to design your own output stage. A great new single-axis IC from them is their MC58113. Watch this space.Īn established company making complete high-end servo controller IC's is Performance Motion Devices ( ). #Large servo motor arduino generator#Trinamic is just starting to innovate here their TMC-4670 BI is their very first brushless servo controller product, although it lacks a trajectory generator ( ). #Large servo motor arduino code#To the best of my knowledge, there is no available code out there to do this to do it properly, at high precision, is actually very complex. Servos are another matter, especially if you want to drive three-phase brushless motors, including direct drive. #Large servo motor arduino free#Trinamic also goes out of their way to provide free schematics of their eval boards, complete code suites, IC footprint files for PCB CAD programs, etc. A complete listing of their motion IC's is here: . Better yet, here is a single chip, two axis stepper controller and driver, with built-in trajectory control with six-point ramping, if you are willing to put a small microcontroller upstream to build their 40 bit "datagrams" (it has step and direction inputs if you don't). They have great step and direction input micro stepping drive chips, such as the TMC-2130-TA (). These are ideal for driving telescope mounts, and are very easy to drive and control, especially with the awesome products from Trinamic ( ). ![]() Before I get to servos, though, a word for steppers. I have worked in precision motion for 37 years. ![]()
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