4. Control Pedals - Part 1

Let us have a look today on “Foot Operated Control Pedals” in the vehicle..

Introduction:

It is often said that the vehicles should be designed from inside out. This refers to the overall packaging of occupants along with controls which give at most driving pleasure. The main objective of this article is the factors considered by the designer during foot operated control pedal design.

Control Pedals; an overview:

Depending on type an automobile may have two, three or four pedals. The arrangement is the same for both; Right Hand Drive and Left Hand Drive vehicles.

A. Throttle Pedal (known as the "Accelerator" or "Gas pedal") is operated by the right foot.

?It is usually narrow and close to the car floor allowing the driver's heel to rest on the car floor. It has a fail-safe design in that it automatically returns to the idle position when not depressed by the driver. There is no foot rest on the right, not even in cars with cruise control.

B. Brake pedal is operated by the right foot, which is sometimes wide and elevated above the car floor. Brake pedal is used to operate the brakes to slowdown or to stop the vehicle. Switch/sensors are provided to give signal to stop lights & ABS ECU.

C. Clutch pedal is operated by the left foot (not in the case of automatic transmission where there is no clutch pedal). Clutch pedal along with operating mechanism engages or disengages the engine from the transmission and drive wheels allowing operator to change the gear. It also helps to start or march the vehicle smoothly from rest.

Clutch has to operate intermittently by the left foot only (or has no function in an automatic vehicle) so sometimes a foot rest is also known as dead pedal (fourth pedal) is provided to the left most side of the pedals.

Vehicle Ergonomics:

Before designing of any pedal, one should have a knowledge of vehicle ergonomics, which affect the comfort of driver.

H-point (Hip point) or SgRP : The main reference point for the occupant and one of the major datum points for the vehicle packaging. Often refer to as the “Seating Reference Point (SgRP). it is always located on the comfort curve.

BOF (ball of foot) for A, B, C point: Located on the pedal plate plane. A main reference point for frontal impact crash space measurement.

AHP (Accelerator Heel Point): The heel point location is often referenced to define the floor and step in height.

Ankle angle: The angle measured between leg shank and foot at the ankle point is referred as ankle angle.

Knee angle: The angle measured between leg shank and thigh at the knee point is referred as knee angle.

Figure shows angles of comfort for vehicle seating.

Generally, followings are angle need to be taken care while designing the control pedals.

Ankle angle: 85° to 110°

Knee angle: 95° to 135°

Leg angle: -5°to +20°

Leg twist angle: -15°to +15°

Let us discuss on “Pedal Positioning & Spacing” in the next article.

References:

1.    AIS-035 (Foot Controls Standard)

2.    Websites on ”Vehicle Ergonomics”