I need to build a device that turns a Leica corner cube reflector (https://shop.hexagonmi.com/emea/nl/EUR/Catalogus/Laser-tracker/Reflectors/Red-Ring-Reflector-1-5"/p/575784), so that it always faces the sensor regardless of how the plaform the reflector is mounted on moves. The reflectors are about 4cm in diameter and quite light. The device needs to have absolute position information so that it knows the current orientation when powered on. The maximum rotation speed should be about 180°/s. he device should be quite compact. I have 5, 12 and 24 V avaiable to power the device.
Could you recommend a motor and sensor or a combination that would work for this?
Both are difficult problems, especially indoors. How do you plan to solve them, and what accuracy is required?
I meant absolute rotational position of the rotation device. Assume I have the desired orientation of the reflector in the coordinate frame of the rotation device as a given. I am just looking for advice for a combination of motor and absolute rotary encoder. 3° to 5° should be fine. Better is a bonus but not necessary.
In case you are interested: this is for my master thesis in engineering geodesy. The topic is to use data-driven methods to estimate the dynamical system of a Husky A200 UGV. This is also called model discovery and consists basically of a regression problem of fitting the derivative of a statevector to the statevector itself (ordinary differential equation describing the observed system). The Husky drives around while being observed by a Laser Tracker and a Totalstation, creating a time series of state vectors. And the two sensors aim at retro reflectors, the thing I need to turn so that it always points at the instrument. Because I observe two points on the Husky I always know its position and orientation of the robot. Obtaining the needed rotation angle of the reflector is just a question of simple coordinate transformations.
Servocity has a decent collection of pan/tilt platforms.
I don't exactly understand your requirements and I'm not an expert in robotics but most pan & tilt mechanisms use servos or stepper motors.
A servo is an angle motor (it turns less than 360 degrees) that has a built-in motor driver and it always "knows where it is" so you just have to supply power and send the control pulse telling it where it should be.
A standard stepper motor is typically 1.8 degrees per step (200 steps per revolution) but they can be geared-down for more precision. You need a "home" sensor (and sometimes a "limit" sensor, and you have to provide the motor driver circuit. When the system starts-up it seeks the home position and then your software simply keeps track of the steps so it knows where is.
A specific recommendation would depend on the mass of what you're moving and the drivetrain connected between the motor and that load. At 180 deg/second, a 200 step/revolution stepper motor would only need to move 100 steps/second which is pretty slow. Assuming we have similar definitions of "pretty light," one of the hobbyist-grade NEMA-17 size steppers should be fine. You'll need to couple it with a home sensor so you have a reference position.