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Texas Instruments The Future of Robotics | 15 Figure 3: Test results showing detection of glass and wall panel. Using the demo software and visualization tools included with the EVM in the mmWave Demo Visualizer, the results shown in Figure 3 clearly demonstrate the mmWave sensor detecting the glass wall surface, as well as the wall behind the glass. Using mmWave sensors to measure ground speed Accurate odometry information is essential for the autonomous movement of a robot platform. It's possible to derive this information simply by measuring the rotation of wheels or belts on the robot platform. This low-cost approach is easily defeated, however, if the wheels slip on surfaces such as loose gravel, dirt, or wet areas. More advanced systems can assure very accurate odometry through the addition of an IMU that's sometimes augmented with GPS. mmWave sensors can supply additional odometer information for robots that traverse over uneven terrain or have a lot of chassis pitch and yaw by sending chirp signals toward the ground and measuring the Doppler shift of the return signal. Figure 4 shows the potential configuration of a ground-speed mmWave radar sensor on a robotics platform. Whether to point the radar in front of platform (as shown) or behind the platform (as is standard practice in agriculture vehicles) is an example trade-off. If pointed in front, then you can use the same mmWave sensor to also sense surface edges and avoid an unrecoverable platform loss, such as going off the shipping dock in a warehouse. If pointed behind the platform, you can mount the sensor at the platform's center of gravity in order to minimize the pitch-and-yaw effect on the measurement, which is a large concern in agriculture applications. Figure 4: Ground-speed radar configuration on a robotics platform. Equation 1 calculates velocity under uniform ideal conditions: fd = (2V/1) * cose (1) where V is the velocity of the vehicle, λ is the wavelength of the transmitted signal, q is the antenna depression angle and f d is the Doppler frequency in hertz. Expanding Equation 1 enables you to compensate for velocity- measurement errors for variables such as uneven terrain that result in sensor pitch, yaw and roll and introduce a rotational velocity component. These calculations are beyond the scope of this paper, but you can generally find them in literature.