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Haptic technologies recreate touch sensations by applying a combination of force, vibration and motion to the user. Haptic technologies are also thought to be a $12.8 billion industry by 2022. In automotive applications, it enables the vehicle’s function controls to be replaced by a single interface, whilst maintaining the tactile sensation of each function. The recreated feel of an actual button has also been found to be less distracting to the driver.
In this article, we look at some of the haptic technologies used, namely, eccentric rotating mass vibration motors, linear resonant actuators and piezo haptics sensors.
Eccentric Rotating Mass Vibration Motors
What are eccentric rotating mass vibration motors?
Eccentric rotating mass vibration motors are one of the most widely used haptic technologies. They are very similar to a conventional DC motor and uses the magnetic field from an electrical current to drive an object in a circle. The rotating mass is also off-center from the point of rotation, hence, they are termed ‘eccentric’.
These motors produce an uneven centripetal force which causes the motor to move backwards and forwards. This movement also produces a side to side vibration, i.e. lateral vibrations. The current of these motors runs inside of the magnetic field and the magnetic field applies a force to the rotating mass. Therefore, the vibrational intensity in an eccentric rotating mass vibration motor is dependent on the DC current supplied. Because it is a simple device, there are many types currently available for varying applications.
Eccentric rotating mass vibration motors in the automotive industry
Eccentric rotating mass vibration motors are cheap to manufacture. Whilst they are not incredibly high-tech, they are used in the automobiles to provide haptic feedback in touch screen displays and dashboards, including as central controls for many switches and for built-in satellite navigation systems (Sat Nav). These motors can also be used in central control systems that provide early warning signals to engine overheating and electrical short-circuiting.
Linear Resonant Actuators
What is a linear resonant actuator?
A linear resonant actuator is a type of vibrational motor which utilizes a combination of magnetic fields and electrical currents to create an oscillating force across a single axis. Linear resonator actuators use an alternative current (AC) voltage to drive a voice coil. This voice coil is pressed against a moving mass which is attached to a spring. When the voice coil is at the same resonant frequency as the spring, a magnetic field is generated and the whole actuator vibrates with a noticeable force.
Both the frequency and the amplitude of the actuator can be adjusted by changing the AC input. However, regardless of the input, the actuator must be driven at its resonant frequency to generate a large enough force. As such, linear resonant actuators can only be effectively used in a narrow frequency range; and they are ideal for those who wish to operate in a specific frequency range but still want to produce haptic waveforms.
These actuators are a direct alternative to eccentric rotating mass vibration motors and possess many advantages against these motors. These include more efficient energy storage and enhanced haptic performance.
Linear resonant actuators in the automotive industry
Linear resonant actuators have a couple of functions in automobiles. First off, they can be used in central control devices, where all the different functions and buttons are located within a single control device. Alternatively, they can be used as a safety measure in steering wheels. The sensors can pick up a multitude of variables, from straying over lanes, to driver drowsiness and over-speeding. If the sensors believe that the driver may be in danger, then the actuator will vibrate the steering wheel to alert the driver.
Piezo Haptic Sensors
What is a piezo haptic sensor?
The final haptic technology is the piezo haptic sensor. Piezo haptic sensors utilize the piezo effect to generate vibrations. The piezo effect is the generation of electricity when a material is stressed mechanically. So, when the piezo haptic sensor is under stress (usually through bending or deformation), it generates a vibration.
Piezo haptic sensors are more precise than the inertial sensors detailed above, and this is because they can vibrate at a wider range of frequencies and amplitudes. Additionally, piezo haptic sensors can vibrate in more than one direction, unlike the inertial sensors which are confined to a single axis of vibration.
Piezo haptic sensors require a higher voltage than their inertial counterparts, but the current consumption is less than eccentric rotating mass vibration motors and comparable to linear resonant actuators.
Piezo haptic sensors are also considered to be a HD haptic technology and are easy to integrate. They possess many operational benefits over inertial haptic technologies, including a faster start-up time, higher bandwidth, lower audible noise and stronger vibrations.
Piezo haptic sensors in the automotive industry
As with the other haptic technologies, piezo haptic sensors primary use is in the touch screen within an automobile’s dashboard. However, the vibration can be localized to only vibrate the screen, and therefore the finger of the person using it.
Sources and Further Reading
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