Precision multi-point sensor position and attitude calibration brackets
Disclosed herein are systems, methods, and apparatuses for calibrating sensors of automated vehicles using calibration targets. A bracket holds the calibration targets and attaches to the automated vehicle proximate to a sensor being calibrated. For some sensors, such as GNSS antennas or similar device for receiving location data from a GNSS, a two-target bracket is fixed at the top of the automated vehicle, nearby the GNSS antenna. For IMUs or similar sensors, a three-target bracket is fixed at location of the automated vehicle proximate to the particular IMU, such as a passenger cabin or on the chassis of the automated vehicle. The calibration targets include a retroreflective surface that reflect signals, such as infrared signals, back to a theodolite (or total station). The theodolite or computer includes preprogrammed offset values indicating the relative positions of the sensor being calibrated and each of the calibration targets of the bracket.
1 . A system comprising:
a bracket comprising two or more reflective targets, the bracket configured to be attached to an autonomous vehicle;
a theodolite positioned with line-of-sight access to the two or more reflective targets and lacking line-of-sight access to a sensor of the autonomous vehicle, the theodolite comprising a controller and configured to generate a plurality of calibration measurements for the sensor of the autonomous vehicle according to two or more signal reflections returned from the two or more reflective targets; and
a computing device comprising a processor and configured to:
for each reflective target, identify a preconfigured offset value between the particular target and the sensor;
for each reflective target, generate a calibrating value using the preconfigured offset value and a calibration measurement for the sensor;
generate a calibration setting for the sensor based upon each calibrating value generated for each reflective target; and
calibrate the sensor, based on the calibration setting.
2 . The system according to claim 1 , wherein the sensor includes an inertial measurement unit, and wherein the bracket is configured to be fixed to the autonomous vehicle proximate to the inertial measurement unit of the autonomous vehicle.
3 . The system according to claim 2 , wherein the bracket comprises a first arm and a second arm and comprises three retroreflective targets affixed on at least one of the first arm or the second arm at respective positions relative to a measurement point that is not coplanar with each position of each retroreflective target, and wherein
a first retroreflective target is affixed to the bracket at a second end of the first arm;
a second retroreflective target is affixed to the bracket at a second end of the second arm; and
a third retroreflective target is affixed to the bracket at a point of the bracket.
4 . The system according to claim 3 , wherein the first arm and the second arm form a perpendicular elbow at an intersection of a first end of the first arm and a first end of the second arm.
5 . The system according to claim 1 , wherein the sensor includes a geolocation sensor, and wherein the bracket is configured to be fixed to the autonomous vehicle proximate to the geolocation sensor of the autonomous vehicle.
6 . The system according to claim 1 , wherein the bracket forms a rod and comprises a plurality of retroreflective targets affixed to the rod at respective collinear positions with respect to a measurement point, the plurality of retroreflective targets comprising:
a first retroreflective target proximate to a first end of the rod, and
a second retroreflective target proximate to a second end of the rod.
7 . The system according to claim 1 , wherein the computing device is further configured to:
receive the preconfigured offset via a graphical user interface; and
store the preconfigured offset into a non-transitory machine-readable storage medium accessible to the computing device.
8 . The system according to claim 1 , wherein when generating the plurality of calibration measurements for the sensor, the theodolite is further configured to:
perform an electronic distance measurement (EDM) operation that generates the calibration measurement indicating at least one of distance, position, or attitude based upon a location of the theodolite relative to the reflective target.
9 . A system comprising:
an autonomous vehicle comprising a sensor;
a bracket comprising two or more reflective targets, the bracket configured to be attached to the autonomous vehicle;
a theodolite positioned with line-of-sight access to the two or more reflective targets and lacking line-of-sight access to a sensor of the autonomous vehicle, the theodolite comprising a controller and configured to generate a plurality of calibration measurements for the sensor of the autonomous vehicle according to two or more signal reflections returned from the two or more reflective targets; and
a computing device comprising at least one processor in communication with at least one memory, the at least one processor programmed to:
for each reflective target, identify a preconfigured offset value between the particular target and the sensor;
for each reflective target, generate a calibrating value using the preconfigured offset value and a calibration measurement of the sensor;
generate a calibration setting of the sensor, based on each calibrating value generated for each reflective target; and
calibrate the sensor, based on the calibration setting.
10 . The system according to claim 9 , wherein the sensor comprises an inertial measurement unit.
11 . The system according to claim 9 , wherein the bracket comprises a first arm and a second arm and comprises three retroreflective targets affixed on at least one of the first arm or the second arm at respective positions relative to a measurement point that is not coplanar with each position of each retroreflective target, and wherein
a first retroreflective target is affixed to the bracket at a second end of the first arm;
a second retroreflective target is affixed to the bracket at a second end of the second arm; and
a third retroreflective target is affixed to the bracket at a point of the bracket.
12 . The system according to claim 11 , wherein the first arm and the second arm form a perpendicular elbow at an intersection of a first end of the first arm and a first end of the second arm.
13 . The system according to claim 9 , wherein the bracket forms a rod and comprises a plurality of retroreflective targets affixed to the rod at respective collinear positions with respect to a measurement point, the plurality of retroreflective targets comprising:
a first retroreflective target proximate to a first end of the rod, and
a second retroreflective target proximate to a second end of the rod.
14 . The system according to claim 9 , wherein when generating the plurality of calibration measurements for the sensor, the theodolite is further configured to:
perform an electronic distance measurement (EDM) operation that generates the calibration measurement indicating at least one of distance, position, or attitude based on a location of the theodolite relative to the reflective target.