(Nederlands) Gimbal

Embed_Gimbal_IMG_6551

The Gimbal is an innovative tool for the calibration of temperature dependent 6DoF motion sensors Embed developed this calibration tool for Siri Marine.

POC to product

Embed has started the development of the Gimbal by creating a POC; a Proof Of Concept. With creating a POC, Embed examined in a practical way what the final calibration tool should be like.

The POC became a ‘pan & tilt’ machine, built with wood and prototype electronics. Field tests with the pan & tilt showed that the final calibration tool needed 360 degrees movement in two axes. The pan & tilt could not move in 360 degrees, but only from top to bottom and from left to right. The fieldtest furthermore showed which materials were needed for the calibration tool and the tests showed what the requirements of the electronics are.
After these field tests Embed designed the final Gimbal. The calibration tool is now fully operational. It now calibrates production batches of 6DoF motion sensors.

The purpose of the Gimbal

The purpose of the Gimbal is calibrating temperature-sensitive 6DoF motion sensors. These sensors are used by Siri Marine, for example during salvage operations on ships. The 6DoF motion sensors measure angular rotation and accelaration. The sensors are temperature-sensitive, because they contain MEMS technology. This technology is known for its temperature-sensitivity. Temperature-sensitivity means that when the temperature of the sensor changes, the sensor no longer gives correct measurement results of the angular acceleration and rotation. By calibrating the sensor, the sensor gives the right measuring results, at temperatures from -20 to +50 degrees Celsius. The maximum absolute angular deviation is 0.07 degrees or 1mg.

The operation of the Gimbal

The Gimbal consists of a number of components. These components provide the calibration:

  • mechanics (aluminium);
  • electronics;
  • a PC.

Embed built these components into a climate cabinet. The PC controls the calibration process and takes care of the movements of the mechanics. The elecronics control the communication between the PC and the  sensors that need to be calibrated.

The calibration process is as follows:

  • The operator places the sensors in the Gimbal. The mechanics contain 3 compartments. In each compartment there is room for two sensors.
  • The Gimbal starts the calibration process. This process takes 24 hours.
  • The Gimbal moves sensors in 360 degrees in 2 axes and heats and cools the sensors from -20 degrees Celsius to +50 degrees Celsius.
  • The Gimbal measures the angular rotation at all the different angles and temperatures.
  • When the measured angular rotation does not correspond to the actual angle of the sensor, the sensor is inaccurate. The calibration tool then automatically adjusts the sensor by sending new parameters to the sensor.
  • The Gimbal tests whether the sensor now shows the correct angular rotation.
  • Once the sensors have a maximal measurement deviation of 0.07 degrees in all angles and at all temperatures from -20 to +50 degrees Celsius, the sensors are calibrated.

The Gimbal not only calibrates the sensors, but also qualifies them. After the calibration it’s apparent how good the sensor was produced. The customer receives a rapport of these findings.

Heating and cooling

During the development it was a challenge for Embed to cool the sensors to -20 degrees Celsius and then warm them to +50 degrees Celsius. It was a challange, because the mechanics were not allowed to get warm. When the conents of the cooler is cold and then suddenly warms, not only the sensors warm, but also the mechanics. Warmed mechanics expands. The angular rotations the mechanics do are then inaccurate and as a result the sensors are not properly calibrated.
Embed solved this by only heating the sensors and not the mechanics, using local heating elements. During the calibration proces the cooler remains on, so the mechanics keep a constant temperature.

Remote operation

The Gimbal can be operated remotely. The calibration takes 24 hours and because it can be operated remotely, the operator does not have to be present during the whole calibration process. Merely placing the sensors in the tool is done manually. After placing the sensors it is safe to run the calibration unmanned, because the tool provides self-diagnosis with errors. The machine performs constant sanity checks to check the process. When an error occurs, the machine stops automatically. 

Results

Already a number of production batches are calibrated with the Gimbal. The sensors have a high accuracy, thanks to the calibration process which takes only 24 hours. The high accuracy of the sensors is a positive development for Siri Marine, since a high accuracy is of great importance in the marine and maritime sector.