The present invention relates generally to vehicle steering wheels and, more specifically, to systems and methods for providing control functions on a steering wheel.
A steering wheel provides a convenient location to present controls to a vehicle operator. For example, a steering wheel may include a number of control elements with each being configured for effecting control over one or more vehicle functions or features. Unfortunately, available space on the steering wheel limits the size and/or quantity of control elements that may be placed on the steering wheel.
In addition to constraints related to availability of space, other constraints may be imposed by the need to carry signals dispatched from each control element through the structure of the steering wheel to a control apparatus located off the rotating portion of the steering wheel. In many steering wheel applications, an electrical signal from each steering-wheel-mounted control element is transmitted from the rotating portion to a non-rotating portion via a sliding contact apparatus such as a slip ring (a series of spring arms that contact and follow a corresponding track as the steering wheel rotates) or a hard-wired connection such as a clock spring, wire coil, or wire tape (each of which including a series of wires wrapped about the steering wheel axis, with the wires being wound and unwound as the steering wheel rotates). In each of these cases, the quantity of electrical connections (i.e., leads) is limited by the necessity to transmit signals from the rotating portion of the steering wheel to a non-rotating portion for processing by a control apparatus such as a vehicle body controller.
In a conventional system, each control element (e.g., push button, toggle switch, slider, dial, etc.) dispatches a signal to be processed by the control apparatus so as to affect control over a single, unique vehicle function or feature. Where signals from more than one control element are to be carried over a single connection to the control apparatus, a system of prioritization (e.g., whereby only the highest priority function is activated whenever more than one control element is asserted simultaneously) must be pre-programmed or hardwired into the circuit.
For example, a conventional resistive switch ladder may be configured such that the actuation of the switch element of the highest priority would results in an output voltage corresponding to that highest priority switch element. In such a conventional system, regardless how many additional switches with lower priority are actuated, the output voltage will not change, instead remaining at a level corresponding to the highest priority switch. It should be appreciated that, in order to accommodate multiple control elements while avoiding the above-described over-riding of lower priority control elements, a separate control element is required for each feature or function to be controlled. Therefore, while practical considerations of space and transmission capacity may tend to limit the number of control elements that a conventional system can accommodate, the demand for increased functionality, controllability, and user convenience tend to call for an increased quantity of control elements on the steering wheel.
Accordingly, it is desirable to have a system and method for providing control, via steering-wheel-mounted control elements, over an increased quantity of unique vehicle functions and features without increasing the quantity of steering-wheel-mounted control elements.