Autoblog visits Toyota's Safety Lab

bwilson4web · Jul 31, 2010

Autoblog gets seat and simulation time with Toyota's newest safety technology [w/video] — Autoblog

One of the newest facilities at Higashi-Fuji is its crash test building, which includes a new angular multi-vehicle crash setup that allows engineers to crash two vehicles head-on at anywhere between 15- to 90-degrees and at speeds up to 87 mph.
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Full vehicle crash testing is very expensive, and while Toyota conducts some 1,600 impacts per year at its global facilities in Japan, Europe and Ann Arbor, MI, it also does vast amounts of simulation work. Like other manufacturers, Toyota executes hundreds of thousands of iterations of its vehicle simulations. Those simulations are able to predict what happens to the vehicle structure, but until recently, they were unable to measure anything about its occupants.
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Following our look at Toyota's crash testing capabilities, we had the opportunity to go for a spin in Toyota's new advanced driving simulator. At first glance, this unit looks similar to those operated by Daimler and Ford â€“ a platform surrounded by a 7.1-meter dome sits on a hydraulic tilt system. Inside the dome (see first image above), a Lexus LS body is mounted on a turntable and a 360-degree projection system produces a high-resolution driving environment. Toyota has also installed a shaker mechanism at the corners of the car to replicate different road surfaces.
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From the simulator, we climbed into a fully functional LS equipped with Toyota's new pedestrian detection system and a more advanced version of its existing pre-collision system (PCS). Lexus has offered its PCS system on a number of models for some time, utilizing the millimeter-wave radar system originally developed for adaptive cruise control to detect an impending collision. If an imminent impact is detected, the seatbelts are pre-tensioned and the brake calipers pre-filled with fluid so as soon as the brakes are applied, full power is available. If the driver neglects to respond to a warning and hit the brakes, the system will apply the brakes with up to 0.3 g of deceleration, reducing the impact force or eliminating it entirely.
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The two most recent developments we experienced during our Toyota safety walk-through are directly related to the recent recalls of the company's vehicles. Earlier this year, Toyota committed to adding a brake override system (BOS) to all of its vehicles by the end of 2010 as a response to the claims of unintended acceleration. The intent of brake override is to ensure that a vehicle can stop safely and promptly even if the engine is racing. Before testing the BOS, Toyota's engineers wanted to demonstrate that even without it, their vehicles' brakes could overcome engine torque and come to a halt.
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Our final evaluation was the re-calibrated ABS for the company's third-generation Prius. Following last year's introduction of the latest model, some drivers began complaining of a loss of deceleration when the anti-lock brakes activated with a light brake application. This is always a tough area for ABS engineers to handle, and the automaker's standard brake tests are all performed with what's known as a "spike" apply to the brake pedal. In this scenario, the test driver steps hard and fast on the pedal to simulate a panic brake activation.

The problem comes when the driver does a light brake application, during which the upstream pressure may be only 200-300 psi or sometimes less. In this case, the pressure response across the apply valve is far less predictable. Generally speaking, when the wheel speed sensor readings are indicative of this scenario, the engineers are more conservative with the system calibration. Applying too much pressure can easily cause the wheels to lock, leading to instability or rough control. This is exactly the scenario the Toyota Prius engineers faced, and they may have gone a bit too light on the ABS pressure re-apply pulses.

The result is that applying the brake just beyond the threshold of adhesion on a slippery surface would cause ABS to activate with a pressure reduction, followed by noticeably lower deceleration than what was present before activation. The measured deceleration is not that different, with perhaps 0.15 g before and 0.01 g after ABS. We tested the Prius on a wet ceramic tile surface with the original calibration and experienced this exact condition. Then we got into another Prius with the updated calibrations and noticed that the difference was less dramatic and overall deceleration was more consistent.
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This might be a little over quoting but the part about the braking is the first analysis of the light braking effects seen. Perhaps another brake upgrade in the future?

Bob Wilson

Autoblog visits Toyota's Safety Lab

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Autoblog visits Toyota's Safety Lab

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