Micro sensors take on big markets

Written by: Justin Cunningham | Published:

Justin Cunningham investigates how an electromechanical sensor went from guiding munitions to car stabilisation systems

Although it has only been in business for just over two years, Atlantic Inertial Systems (AIS) has already established itself as global experts of micro electromechanical systems (MEMS). And much of its success is down to good engineering and business strategy. It has been able to keep the IP and clever bit of the engineering process largely within the UK, but exploit markets globally.

Its inertial measurement units (IMU) were originally designed to be used as 'gun hardened' guidance systems that would be integrated within munitions and guide them to a target. The technology originated out of work conducted by BAE Systems and in 2007 it was sold off to US investment company JF Layman in 2006 to form a separate company. JF Layman saw massive potential for the MEMS devices in a number of applications and set up AIS to accommodate the military markets and initiated a joint venture with Japanese based Sumitomo Precision called Silicon Sensing to take the devices to the automotive market.

"We have come from a background of fairly large company attitudes and mentalities," says Ian Scaysbrook, chief engineer of AIS. "And we are now getting use to being a small lean privately owned company."

The very different markets require very different approaches to engineering. The military market typically requires the delivery of high quality rugged products and needs a lot of support. The automotive market on the other hand requires high volume products at low cost – but still to a certain quality.

In the design of its IMUs and solid state gyros, AIS has taken advantage of off the shelf technology, but there is a limit to how much this can be exploited – especially for the high performing 'gun hardened' IMU's. Although currently MEMS devices do not offer as good performance as spinning wheel gyros, they are less expensive, a lot tougher and a lot smaller.

When fired on artillery rounds and devices can experience shock levels in excess of 20,000g's – a spinning wheel gyro would simply never survive. But the inherent ring like structure of AIS's MEMS helps to spread the loads though it's housing and makes the sensor inherently more resistant to sudeen shock and vibrations.

"The old spinning mass gyros would not stand a chance," says Scaysbrook. "So to get to that level of performance we had to go back to the raw sensors and do some redesign work.

"We fired four last year and they all hit the target and after were amazed we could do it so reputably. We have performed in excess of 60 firings now and had a 100% success rate – no failures of the IMU at all, which is unprecedented. And there accuracy has improved as well."

And the markets and potential applications keep growing. Ruggedised gyros are to used on the Ariane 5 space launcher, various helicopters, armoured vehicles and even in a soldiers boot. Basically anything that needs to know where it is and which way it is pointing.

The automotive MEMS made by Silicon Sensing are made from cheaper components and don't have the exceptionally high performance of military grade IMU's. The main use in the automotive industry is electronic stabilisation protection systems.

"The gyro essentially acts as a yaw rate sensor," says Scaysbrook. "So if a vehicle goes in to a skid, the sensor can detect the fact the car is rotating when the driver is telling it not to. This will then engage an engine control system that will turn on brakes and adjust engine power to the wheels accordingly to correct the skid."

The joint venture known as silicon sensing has sold over 15 million gyros to the automotive industry. Although price is significantly less than the military variants, the high through put allows the business to be lucrative.

But it is also key to getting the precision for AIS's devices. "It allows us to cream off the best, most rugged and highest performing gyros," says Scaysbrook. "They are essentially the same gyros, but if we were not producing that rate of gyros for the automotive and commercial markets, we just would not be able to do that, it wouldn't be cost effective."

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