# Motor position using linear absolute encoder

Hello guys .
I am having this project of controlling 3 phase AC motor using an encoder via an HMI .
I am having problem selecting the right encoder and an HMI and righting a program to control the motor via the encoder. In such a way that if I put 200mm the motor will stop at that position

Can you provide some more details? Selecting the right encoder and HMI (Iâ€™m assuming this is Human Machine Interface; please correct if something else) depends greatly on the scale and scope of the problem.

Encoder questions: How big is the thing that is moving, how strong is the motor, how fast are things moving?? Is it going on wheels, a lead screw, rack and pinion, or what? What is the required range of motion (distance one end to the other)? What is the required resolution/tolerance (10 cm, 1 cm, 1mm, 0.1mm, etc?) .

HMI: Again, how big is the thing that is moving? WIll the user be riding it, standing/seated right next to it, or located remotely (and if so, how remotely)? Do you expect that desired positions will be entered numerically (keyboard), analog (e.g. joystick or slider), or both?

Are there any other pre-defined constraints (e.g. a required computer, computer language, or comms link, damp/dusty conditions)?

1 Like

The motor is 380v ac motor with 3.2KW. the motor is fitted with a pulley and a lead screw.
The required range of motion is around 3Meters and the required resolution is around 0.01mm.
HMI:
The user will be controlling the distance covered by the motor using the HMI and numerical keyboard.
I am still working on the constraints. I am a rookie i donâ€™t know much and am still learning.

You really need more than internet advice for something like thisâ€¦ But. There is wide range of linear encoders. Picking the right one really depends on the physical environment. The next question is where the control is happening. These days you can buy motor drives that have PID and logic built in. Then you can buy a simple HMI that is capable of talking to the drive. What components you use depends a lot on which automation supplier your company uses.

Edit: I did not pay attention to your required accuracy. You are going to need vendor specific advice for your encoder. I am not sure if you are going to get there with a standard open loop 3 phase motor and drive.

1 Like

These are the numbers that make the project a â€śbuy COTS

â€ť rather than â€śRoll your own with Arduinoâ€ť. Itâ€™s also definitely outside the realm of anything FRC
folks would for sure have expertise in.

If you donâ€™t have any constraints, AutomationDirect is a great supplier to FRC

that would love your business! Their GS3 Series motor drives may fit part of the bill.

Disclaimer: Though I technically have a degree in EE, I found the above link via google, and have never done anything remotely close to this project. 100% buyer beware.

Wow. Iâ€™ve never worked at this scale, and agree with @FrankJ and @gerthworm youâ€™ll need better advice than I can provide. The only thing I can think of straight away that might fill this bill would be encoders used to guide large CNC routers.

Do you have a cost range for this? Is there someone with software experience working with you on this to design the controller itself, or is it just you? There are multiple solutions you could go for, but some can get pretty expensive, and others could be pretty difficult to implement. If you know more about the physical system â€“ is the pulley under a load such that itâ€™s likely to slip, are there suitable mounting locations for additional sensors, are there any space constraints at the mounting site of the encoder, etc. â€“ it could help restrict the problem a bit more.

This topic was automatically closed 365 days after the last reply. New replies are no longer allowed.