subject: Capacitive Sensing - Ushering in a revolution in Automotive HMI design [print this page] Capacitive Sensing - Ushering in a revolution in Automotive HMI design
Introduction
The increasing numbers of electronic systems in a car have ushered in a revolution which has transformed the car into a safe, luxurious and intelligent machine. One thing that has not changed however is the importance of human interaction with the car. This interaction defines the user experience and is a key marketing differentiator between different vehicles.
The systems measuring and tracking interactions of the user as well as providing feedback are collectively known as Automotive Human Machine Interface (HMI) systems. From the user's perspective, this interaction maybe conscious - when he deliberately provides input to a system, or subconscious when the system measures his intent without his knowledge.
Capacitive Sensing Ushering in a revolution in Automotive HMI
Even with the inherent barriers in the adoption of new HMI technologies in the automotive environment, engineers are constantly trying to improve HMI systems to make them more intuitive, look cooler, and be more accurate. At the heart of this change are innovative human interaction sensing technologies which are enabling this evolution. One such technology is capacitive sensing which has revolutionized the design and implementation of HMI applications.
Very simply, a capacitive sensor is composed of a pair of adjacent electrodes.
When a human being (or any other conductive object) comes in proximity to these electrodes, there is additional capacitance between the electrodes and the object which can be measured to detect the object's presence.
Using this technology, it is easy to build touch sensors acting as buttons, sliders, trackpads etc.
Alternately capacitive sensing can also be used for proximity sensing where no contact is required between the sensor and the user's body. This can be achieved by increasing the sensitivity of the sensors. Further, such sensors are non-line of sight; therefore, a single sensor is enough to detect approach in 3 dimensions.
Such a technology becomes even more powerful in conjunction with programmable mixed signal controllers. Such devices enable the measurement of capacitance intelligently enabling the detection of human proximity in terms of range, direction of approach, gesture recognition etc. They also enable the possibility of integrating other functions like controlling motors and LEDs to provide feedback to the user based on touch/proximity.
Center console design models:
The Brick Design Model
Center consoles have been traditionally designed using the brick design model. In this model, each center console component is a complete unit comprising of controls/switch panel as well as the actual electro mechanical box.
For example a center console is composed of a number of independent components comprising the HVAC, Audio, and Navigation units. Each individual component is a complete system comprising the controls, electronic components and mechanical actuators etc.
The limitations of such a design is that each system is developed in a silo, and the car manufacturer has only limited control in being able to provide a uniform look and feel. The designers also have limited freedom to design center consoles with restrictions on styling. There is also an increased cost adder to allow for tooling costs associated with additional grooves and harnesses. Due to an increased number of mechanical components, there is also an increased chance of failure.
The integrated design model
In the integrated design model, the control for all elements of the center console are unified into a single front panel with the actual electro-mechanical systems connected through a data bus. The distribution and integration of the control panel enables HMI designers with greater flexibility in styling as well as greater control over uniform look and feel. Such a design also reduces tooling charges and increases reliability. Because of integration and reduction of controls, such designs also reduce the total cost of systems.
The integrated design model is largely made possible because of capacitive touch sensing. Designers can integrate a flat panel with capacitive sensors, and have greater freedom to play around with curves thereby provide a better overall styling of front panels. Due to the reduced number of mechanical components and fewer grooves (which trap dust etc), such designs also enhance reliability and reduce system costs.
Conclusion
From making infotainment systems cooler to providing a reliable methodology for measuring liquid levels, capacitive sensing is proving to be an immensely popular and useful sensing technology for use in the automotive applications. Its potential is just beginning to be tapped with next generation mixed signal controllers which are designed for the automotive industry. As systems get more demanding, designers will find that this technology provides an effective sensing technology for a wide gamut of applications.
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