Ultrasonic 3D Motion Capture (Orientator) | Hackaday.io

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Ultrasonic 3D Motion Capture (Orientator)

6DOF tracking at extremely simple and cheap !<br>The computational load is light !<br>It can be used in places where light cannot be used !

Yohei Inada

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Yohei Inada

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Development of Airborne Ultrasonic Motion Capture

MISC

researching project

virtual reality

Motion CapturE

ultrasonic

3-sided measurement

low cost

spatial measurement

vr tracking

3d input device

6dof

This project was

created on 06/18/2026

and last updated 7 days ago.

Description

"All opinions expressed here are my own and do not represent the official views of my employer. On the other hand, I obtained approval from my employer for presenting at the academic conference (JSME). Basically, the information provided will be limited to what is stated in the announcement."

We have developed a spatial dimension measurement device and motion capture (orientator) using airborne ultrasonic waves. We achieved spatial measurement by using 3 ultrasonic transducers and 3 ultrasonic microphones. The measurement principle is based on 3 sets of 3-side measurements. We acquire plane equations of microphones and transducers, and calculate the orientation angle and direction based on the surface normal vector. It is expected that this device can instantly measure the positional relationship of pipes, etc. at plant construction work with displaying the 3D data on PC in real time.

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6DOF tracking at extremely simple and cheap !<br>The computational load is light ! It can be used in places where light cannot be used !<br>How about using it as a VR controller ?<br>Alternatively, it can be used, for example, to measure spatial displacement or alignment of piping during plant construction.

We achieved spatial measurement by using 3 ultrasonic transducers and 3 ultrasonic microphones. The measurement principle is based on 3 sets of 3-side measurements. We acquire plane equations of microphones and transducers, and calculate the orientation angle and direction based on the surface normal vector.<br>Current specifications are as follows:<br>Table 1 Examination result and performance of apparatus<br>Performance Item Value Spatial dimension measurement rangeAbout 1000 mmMotion capture operating rangeAbout 700 mmSpatial dimensional accuracyAbout ±1 mmMeasurement angle accuracyAbout ±1 °Frame per Second (FPS)About 13 FPSMismeasurement rate (MAX.)5 FPS* * Depends on the device's speed, position, direction, and orientation.

--Extending the measurable distance range for spatial dimension measurement<br>In Table 1, the measurable range is approximately 1000mm, but over 2000mm is desired for plant sites. To extend the range while maintaining accuracy, it is necessary to improve the S/N ratio by increasing transmitter output, enhancing receiver sensitivity, and optimizing cross-correlation methods for the transmitted and received waveforms. Optimization of the number of integrations for reception data is also required.<br>--Improving performance for motion capture<br>As shown in Table 1, motion capture performance features a range of 700mm at 13 FPS, with errors in convergence calculations at a maximum of 5 FPS. To enhance work safety by monitoring during pipe movement, increasing the frame rate and decreasing convergence errors are necessary. This includes investigating transmission waveforms that are easier to identify [9] and improving the numerical calculation routines for Newton's method to ensure more reliable convergence.<br>--Supplying the device at a lower cost<br>Compared to optical motion capture, this ultrasonic device has fewer parts and lower computational loads for 3D drawing and iterative calculations. To supply it more cheaply, we plan to replace general-purpose FPGA boards with dedicated circuits, minimize part counts, and implement MEMS technology for transmitters, as receivers already use MEMS microphones.

We demonstrated that spatial dimension measurement and motion capture can be configured with ultrasonic waves, allowing positional relationship measurement by...