Pedal Box Design / Drive-by-Wire

With the ever increasing significance of performance in impact, car manufacturers are looking carefully at traditional elements of vehicles and their specific behaviour under crash conditions. One very significant element is the pedal box. Where the pedals are held and pivoted, a rigid structure is typically required; in impact, the pedal box can be forced in on a driver’s lower leg and feet leading to significant injury. Several ways to resolve this have been tried or are under consideration including alternative pivot points, collapsible pedal boxes, breakable pedal connections and more complex arrangements that bypass direct mechanical connections.   In an article for MIRA New Technology, Fernando Burguera of Batz, S. Coop, explains how designing for EuroNCAP is becoming a practicable industry standard and how manufacturers are looking to suppliers to help them tackle crash performance component by component. Drawing upon the current EuroNCAP testing procedures and anticipating ongoing raising of the bar, Batz, S. Coop. built a list of specifications in order to design new pedal box systems: Zero forward movement (possibly some backward movement) after collision No entrapment of the foot Immediate activation No accidental activation Functionality after impact; it may still be necessary to brake even after impact Vehicle independent; the system should be self-contained The full article can be found here.   Drive-by-Wire A more costly and complex solution to the issue of pedal box crash performance is to attempt to remove significant mechanical components and supporting structure. This is done by replacing direct mechanical connections with electronics which act as a proxy between the driver’s input and the actuation of driving controls, namely accelerator, brakes and clutch. Any such system involves the sensing of user input and consequently relaying that to servos and actuators. The benefits include the simplification of structure in the pedal area and the possibility of computer correction for control errors. Detrimental factors include a substantial increase in component cost and complexity including increased manufacturing and maintenence cost.

An example of a proxy control is the Valeo Clutch-by-Wire. The unit replaces the mechanical link between clutch and pedal with an electrical clutch actuator, an electric clutch pedal and an electronic control unit (ECU). A pedal sensor measures the position of the clutch pedal and transmits this information to the ECU which also receives information about car behavior. The ECU in turn controls the clutch actuator and depending upon the driver’s wishes, the system can not only correct driver mis-operations but offer complete clutch automation. The system is designed to require lower stroke and effort to the pedal and improves pedal feel with “virtual” resistance to foot pressure. More compact than a conventional clutch actuation, the Clutch-by-Wire system improves driver crash protection since it enables an optimized, less intrusive, pedal box design.


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