The Spirit of Monozukuri—5 The Spirit of Monozukuri—5
The Story Behind the Development of the Anti-lock Braking System The Story Behind the Development of the Anti-lock Braking System

Design the World’s Smallest ECU. The Fight over a 0.1 Ω Resistance. Design the World’s Smallest ECU. The Fight over a 0.1 Ω Resistance.

Let's take a look at what the team did to deal with the resistance of a solenoid valve.
It turned out that a minimum of 5 Ω resistance was needed to combine a drive power IC into the main IC. They tried in vain to increase the resistance.
The project members had no choice but to reconsider the layout from scratch, both the board and inside the IC.

Testing repeated with different resistance values incremented by 0.1 Ω to determine the best one.

The highest possible resistance is what the ECU board designer wants for the solenoid valve drive power IC.
On the other hand, the solenoid valve designer prefers to keep the resistance lower.

“Just another 0.1 Ω increase. What would you say?”
The ECU board designer asks.
The solenoid valve designer replies, “Any increase may disturb the intended behavior of the valve. It's already at the upper limit.”
It was an intensive fight over a 0.1 Ω resistance.

Struggles develop strengths and make things perfect. They found an ideal combination, 8.6 Ω and 4.3 Ω, would work to meet the design requirements.

What was turned out was an ECU board, just a bit bigger than a business card.

Today, the ECU configuration employing a built-in power IC designed by the team is the mainstream of ECUs for ABS.

Downsized ABS Module Downsized ABS Module
Downsized ABS Module
Right: E-ABS, 4.5 kg in weight, released in 1992
Left: GA21, 1.7 kg in weight, released in 2000

The Relationship between Voltage, Current and Resistance

The more resistance given, the less current flows.
For a smaller profile, the ECU board designer needed to increase the resistance. Contrary to that, the valve designer wanted to keep the resistance low, to secure enough current to operate the solenoid valves.

Current I (A) = Voltage V (V)/Resistance R (Ω)

The World’s Most Compact, High-performing ABS is Born. The World’s Most Compact, High-performing ABS is Born.

After the ECU, the hydraulic unit became the focus of downsizing. New technologies were poured into the project and hydraulic lines were redesigned. The unit that came out from the project in March 2000 was both less than half the volume and weight.
The ABS module, renamed the GA21, was finalized.
And, it was the world's most compact, high-performing ABS fitted with an ECU.
The GA21 became the choice of auto manufacturers. Toyota's Vista and Opa, Mitsubishi’s Pajero io, and Daihatsu’s Terios—all these mass-produced cars employed the GA21 for their ABS.

In 2001, ADVICS was created as an independent group company.
Divisions engaged in the development and sales of brakes and brake systems were all handed over to the new company. From Drivetrain Engineering, many of those who shared the years in creating the GA21 ABS joined.

At Aisin, Production Promotion continues to manufacture ABS modules.

Some comment, “In recent years, more and more automobile manufacturers have preferred suppliers capable of providing entire system packages rather than individual components.
Serving as a system supplier, ADVICS benefits Aisin Seiki, bringing more opportunities to sell ABSs and other brake systems and components.”

As the technology inside automobiles continues to grow more sophisticated, Aisin takes actions anew to develop new features by applying its expertise in brake systems to electronic stability control (ESC).

ADVICS
Established in July 2001, by Toyota Motor Corporation, Denso Corporation, Sumitomo Electric Industries, and Aisin Seiki. Develops and sells automotive brake systems including ABSs.
Electronic stability control (ESC)
A computerized technology that improves a vehicle's stability by detecting and reducing the loss of traction (skidding). When ESC detects loss of steering control, it automatically applies the brakes to help steer the vehicle where the driver intends to go.