Gyro
stabilizer
A laser diode is held within the center tube. A MEMS gyro is mounted on the outer aluminum box. Angular motions of the box are picked up by the gyro and used to command an angular correction of the tube.
Rare earth magnets
attached to the tube are pulled by electromagnets, forming a voice-coil
actuator that deflects the tube. Motion of the tube cancels motion of
the box.
This is the amplifier for driving the voice coil actuators. A bipolar design provides a voltage between +2 and -2, so the coils can attract or repel the magnets.
The inductance of the coils caused an instability, so an RC shunt to ground was added (see circuit diagram)
Here you can see both the vertical deflection actuators (front, right) and horizontal deflection actuators (rear, left).
The coils were hand-wound onto custom brass spindles, and attached to the aluminum box with brass screws. Steel springs were also custom-made and placed coaxially with the magnets. The spring constant was made small enough to permit a large deflection range, but large enough to prevent low-lying resonance frequencies.
The control system is programmed in Simulink. Software integrators convert the angular rate signals of the gyro to angular position signals, which are amplified to give the actuator voltages.
Mechanical drawings, programs, and circuit diagrams
This 1.5MB Quicktime .mov video (MPEG4) shows the laser tube moving opposite to the motion of the housing, to counteract it.
This 1.5MB Quicktime video shows the actuated laser dot (upper) and the reference laser dot (lower) as projected onto a wall.
First the control system is off, and the two dots track one another. Then the control system is switched on, showing the actuated laser dot stabilized.