Positional and Inertial Aiming

Potentiometer guns, IMU aiming and optical-inertial fusion.

Firearms

Positional and Inertial Aiming · Deep Dive

Positional and Inertial Aiming

Aiming without seeing the screen.

Potentiometer guns, IMU aiming and optical-inertial fusion.

Photo: PlayStation Move Sharp Shooter by Evan-Amos

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    Volumes

    1. Vol 1 Aiming Without Looking — What Position and Motion Sensors Actually Measure A light gun needs one number pair: where on the screen the barrel points. A camera in the gun measures it; angle sensors, gyroscopes, accelerometers, magnetometers and room trackers each measure something else and have to infer it. The map of the methods, the geometry that turns an angle into a pixel, and why every one of them ends up needing an absolute reference
    2. Vol 2 Angle Sensors on a Mount — Potentiometers, Gears, Magnets and Encoders The engineering under the arcade's fixed guns: how many distinct readings each sensor gives across a screen, why the arcade geared its pots, what a 12-bit magnetic angle sensor really resolves when its range is narrowed, why the angle-to-screen map is a tangent, and which sensor a mounted gun built today should use
    3. Vol 3 Gyroscopes, Accelerometers and Magnetometers — What the Datasheets Say, in Pixels How a MEMS gyroscope senses rotation; three current six-axis parts compared from their datasheets; why bias, not noise, is what drifts, worked through in pixels on a 55-inch screen; what an accelerometer can and cannot tell a gun; and why a magnetometer inside a gun with a 24-volt solenoid is no reference at all
    4. Vol 4 Sensor Fusion — Complementary, Mahony and Madgwick Filters, and the Gyro over an Optical Fix How a fast sensor that drifts is tied to a slow one that does not: the complementary filter and its one parameter, Mahony's integral term that learns the gyro's bias, Madgwick's gradient step; how the Wii MotionPlus, PlayStation Move and Freespace pointers used gyroscopes beside an absolute reference; and why a light gun needs far less than a full orientation filter
    5. Vol 5 Other Ways to Find a Gun in a Room — Cameras at the Screen, Ultrasound, Magnetic Fields, UWB and Optical Flow The position half of the aiming problem, and every published way of measuring it that is not a camera in the gun: what the PlayStation Move, the Power Glove, the Razer Hydra, ultra-wideband radios and mouse-type flow sensors actually measure, how good their makers say they are, and what that accuracy is worth at 2 m from a 55-inch screen
    6. Vol 6 An IMU for This Gun — What It Adds, Which Part, and What It Costs on the Pico Nobody has shipped a light gun with a gyroscope in it. What one could add to the OpenFIRE gun with the PAJ7025R3 camera — bridging lost markers, telling off-screen from lost, gesture reloads, seeing the recoil kick — ranked by value; four candidate parts compared, with why and why not; where it fits on a Pico with no free pins; a firmware sketch; and the bench tests that decide it