Vertical Reference Units (VRU)

VRU’s for USVs & UGVs

3DM-CX5-15 VRU High Performance Tilt : Vertical Reference Sensor by Parker Hannifin

Vertical reference units (VRUs) are inertial sensors that are used to measure roll, pitch and yaw for platforms such as USVs (uncrewed surface vessels), UGVs (unmanned ground vehicles) and other robotic platforms. They are typically made up of an IMU (inertial measurement unit) with extra filtering and algorithms, and are often deployed when the full functionality and high accuracy of an INS (inertial navigation system) is not required.

VRUs typically incorporate three accelerometers and at least two gyroscopes. The gyroscopes are used to measure angular velocity, while the accelerometers measure acceleration due to gravity which is used as a reference without any geographic or magnetic input. As they do not rely on a magnetic reference, VRUs are ideal for use in applications where magnetic interference may be a factor.

Vertical Reference Units & MRUs

VRUs may be incorporated into more complex devices known as Motion Reference Units (MRUs), which in addition to roll, pitch, and yaw, also output the ship motions of heave, surge and sway, making them useful for marine and maritime applications.

Vertical reference units are often used for roll damping and heave compensation in USVs and other vessels. They may also be used for stabilization of platforms as well as GNSS and communications antennas.

Tactical & Industrial VRU Sensors

VRU sensors may be available in a variety of grades, including industrial and tactical, to meet a range of accuracy and precision requirements. Data may be output via a range of methods and protocols including UART, USB, serial and wireless.

Since they are often used on board vessels, VRUs may have to be ruggedized for marine environmentals. They may have corrosion-resistant housings and may be IP-rated to withstand splashing or immersion in water.