Inertial sensors vital to Mayflower autonomous voyage

Compact inertial sensors from Silicon Sensing vital to Mayflower autonomous voyage

  • Precise motion data from silicon IMUs advises vessel manoeuvring
  • Devices also assist measurement of ocean surface

The Mayflower Autonomous Ship (MAS) is set to re-embark on its three-week trans-Atlantic journey in April 2022 equipped with two Silicon Sensing’s AMU30 inertial measurement units (IMUs). These Silicon Sensing AMU30 devices send highly precise motion data to the new ‘AI captain’ that guides the vessel. They also assist in measuring sea surface height as part of detailed scientific analysis of ocean topography.

Brett Phaneuf, co-director of the project comments: “The AMU30s have been bullet proof deployed in extremely challenging conditions and are vital to the Mayflower Autonomous Ship’s mission to collect highly resolute data from the world’s oceans.”

Steve Capers, General Manager of Silicon Sensing Systems comments: “This is an extraordinary project and we are proud that our small, rugged IMUs are at the heart of both the control of the vessel and the gathering of data that will further our knowledge of the oceans.”

AMU30 is a micro electro-mechanical system (MEMS) unit with impressive inertial performance, including exceptional bias stability and low noise characteristics, plus an embedded Kalman Filter based AHRS (attitude and heading reference system) algorithm. It delivers precise 3-axis outputs of angular rate and acceleration, plus roll, pitch and heading angles, altitude and pressure, and temperature, at 200Hz – all critical to precise maritime navigation.

Phaneuf explains: “The two AMU30 are used to make real-time, precision measurements of the movement of the Mayflower Autonomous Ship in 6 degrees of freedom (DOF) so that the AI Captain may make minute manoeuvring adjustments to optimise vessel performance in a complex wavefield, while also providing redundant general navigation capability at sea.”

He continues: Furthermore, when coupled with optical and RTK (real time kinematics) GPS information, the AMU30 assists the ship in making highly accurate measurements of sea surface height. Accurate measurements of ocean surface topography are important for studying ocean tides, circulation and the amount of heat the ocean holds.”

The MAS journey across the Atlantic will celebrate the voyage of the original Mayflower some 400 years ago. It is just one element of an extensive scientific data gathering and research programme the vessel will complete in the coming years. The ship is guided by its new AI Captain, built using IBM cloud, artificial intelligence (AI) and edge computing technologies, and uses a hybrid engine that draws on solar power. Working with scientists and other autonomous vessels it provides a flexible platform for deepening understanding of issues such as climate change, ocean plastic pollution and marine mammal conservation. In parallel, the development of marine autonomous systems such as this will transform ocean-related industries such as shipping, oil & gas, telecommunications, security & defence, fishing & aquaculture.

DMU11 enables Precision Agriculture

DMU11, the latest miniature Inertial Measurement Unit (IMU) from Silicon Sensing Systems Limited, is now in full production and has been selected by Agrifac Machinery BV for use in their latest cropsprayer, the MountainMasterPlus.

DMU11 is the latest in a family of high performance IMUs, offering market-leading inertial sensing capability in a cost-effective OEM package, and aimed at high volume industrial applications like Smart Agriculture. With each silicon MEMS sensor being made by Silicon Sensing in their foundry in Japan, the DMU11 combines three rotation rate sensors with six linear accelerometers. Sophisticated processing is included, allowing each unit to be individually calibrated to optimise its performance over a wide temperature range. Communication is via an industry standard RS422 link.

In Agrifac’s crop-sprayer application, their StabloPlus chassis controls the ride height of each wheel individually, enabling the cab to stay horizontal on steep slopes whilst the spraying boom maintains a fixed height over the crops. DMU11 plays a key role in these control loops, providing reliable real-time inertial data in a challenging real-world environment.

Key performance parameters of the DMU11 are:

  • Dynamic Range ±300°/s and ±10g
  • Bias Instability <10°/hr and 0.05mg
  • Random Walk <0.4°/rt hr and 0.05m/s

Silicon Sensing has a long heritage in the gyroscope marketplace; predecessor companies can be traced back to the first production of rotating gyroscopes for navigation – over 100 years ago. Recently, Silicon Sensing has been leveraging the inherent high performance capability of their particular MEMS sensors with a series of high-performance gyros and IMUs for a diverse range of applications, including autonomous self-driving vehicles.

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