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Corolla Electric Power Steering PE10-008. 16 June, 2010. Outline. Steering Development Steering Testing and Standards Field Information Clarifying Customer Feedback Explanation of “Wander” or “Drift” Simulation & Comparative Testing Toyota Assessment. ’09-10 Corolla Steering Development.
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Corolla Electric Power Steering PE10-008 16 June, 2010
Outline • Steering Development • Steering Testing and Standards • Field Information • Clarifying Customer Feedback • Explanation of “Wander” or “Drift” • Simulation & Comparative Testing • Toyota Assessment
’09-10 Corolla Steering Development • Based on market research and competitor vehicle benchmarking, Toyota aimed to improve: • Steering feel • Vehicle agility • Ride comfort • In dynamic testing, development vehicles compared favorably to other models
Developmental Dynamic Safety Testing Confidential Information Redacted
Developmental Dynamic Safety Testing Confidential Information Redacted
Description of the EPS systemSystem Outline • New for the 2009MY Corolla and Matrix as standard equipment • Utilizes an electric motor and reduction mechanism to provide assist torque to the steering shaft • ECU calculates the appropriate amount of assist to provide to the steering shaft • The benefits include improved overall fuel economy
Description of the EPS systemDesign Concept Confidential Information Redacted
Steering Testing & Standards • Toyota has 3 standards: • Steering effort when slowly operating steering wheel at standstill • Steering effort when quickly operating steering wheel at standstill • Vehicle behavior and steering characteristics before and after EPS fail-safe mode activation • Vehicles surpass all standards above • Also complies with ECE 79 (Europe) and GB 171675 (China) which specify steering effort for normal driving and when steering assist fails.
Steering Effort Criteria • Corolla EPS surpasses regulatory requirements for steering effort under power assist failure Criteria & Recommended Values of Steering Effort
Field Information • VOQ’s - Over 80% of VOQ’s had descriptions of steering “wander” or “drift” • Consumer Complaints - A majority of complaints received by Toyota also appear to generally describe a steering “wander” or “drift” • Warranty - A high percentage of claims involve adjustment (such as wheel alignment) rather than parts replacement • Field Reports - Majority of reports are not related to “wander” or “drift” • Crash Cases - Insufficient information is available on crashes to assess cause, but no defective parts found in those vehicles which were inspected
Clarifying Customer Feedback • Toyota interviewed 107 customers (all submitted VOQ’s) to understand their complaint of steering “wander” or “drift” • 90% described what can be characterized as a vehicle “wander” or “sensitive” steering • Toyota engineers inspected and drove 87 of those vehicles • In all vehicles, no defect was found in the steering system • Steering feel of all vehicles was found to be consistent with design intent and within acceptable production variation with no significant deviation
Explanation of “Wander” or “Drift” • Based on the design concept, the neutral area steering effort is slightly stiff • Vehicle reacts when steering input exceeds the self centering force of the vehicle • When self centering force is exceeded, the vehicle moves according to the steering angle • Some customers may complain of a delay at this transition point and perceive slightly “stiff” steering
Explanation of “Wander” or “Drift” • Based on road conditions and external inputs, some customers may perceive a “wander” or “drift” due to the slightly stiff on-center feel “Drift” “Wander” Cross Wind “Wander” Slant Disturbance Undulation
Simulation & Comparative Testing • Based on 87 vehicle evaluations, Toyota set up a test vehicle • Test vehicle was configured with steering and suspension components considered 3 standard deviations from normal production to represent the most extreme case for stiff steering feel from a design point of view • The test vehicle was evaluated dynamically to assess steering effort and stability • Steering angle and vehicle direction were evaluated against road undulations and compared to other vehicles • Test vehicle compared favorably to other models evaluated
Simulation & Comparative Testing Confidential Information Redacted
Simulation & Comparative Testing Confidential Information Redacted
Simulation & Comparative Testing Confidential Information Redacted
Toyota Assessment • Corolla steering is stable and controllable • “Wander” or “Drift” is perceived by some drivers due to slightly stiff steering “feel” in the on-center position • Steering effort and feel is comparable to a variety of other vehicles • Steering “feel” may be “different” from customer’s previous experience, but is no different than the feel of driving a different vehicle than usual (e.g. a rental vehicle)
Toyota Assessment • No defect is present in the EPS system • The design and performance of the EPS are appropriate and no unreasonable safety risk is presented • This is a customer satisfaction issue that will be addressed by a differently calibrated EPS ECU for those owners who prefer a “lighter” steering feel
Vehicles Available to Drive • Test vehicle (described above) • Repurchased vehicle • Toyota purchased the vehicle (ODI # 10308501) from a customer who complained of “touchy” steering and experienced vehicle “wander” on the freeway • The customer primarily operated the vehicle in the Sacramento, CA area and perceived a “wander” at speeds above 45mph • Customer submitted VOQ after learning from a news story that “this is a real safety issue, coupled with the gas pedal issue” • Toyota evaluated the vehicle and found no defect present in the EPS system