PowerHap™ Actuators

Application Note Devices that Enhance the Safety of the Digital Cockpit

Devices that Enhance the Safety of the Digital CockpitThe methods of use of automobiles will change substantially in the future including autonomous driving and car sharing services, and the human machine interface (HMI) between drivers and their cars will also completely change.
The automobile industry is developing the digital cockpit in pursuit of an HMI that will provide safety and reassurance while freeing drivers from the burdens of driving and allow time to be used meaningfully and in comfort.
Below is an introduction to TDK product and technologies that enhance the value of the digital cockpit with the aim of achieving an HMI that ensures and enhance safety and reassurance through the driver's senses.

The digital cockpit will determine the product value of next-generation automobiles

The cockpits of current automobiles are equipped with an instrument panel that shows the speedometer, tachometer, fuel gauge, water temperature gauge, trip meter, and other information necessary for driving as well as display devices that support the driver such as center information displays that show navigation maps and so on.
The digital cockpit will spur a shift from conventional analog meters to liquid crystal displays, and it is thought that it will be possible to switch between travel information useful to passengers during autonomous driving and information that supports driver operation during manual driving by a driver shown on the same large screen.
Relying solely on the visual appeal of the display, however, cannot achieve both safety in transportation and convenience and comfort.
Achieving level 3 autonomous driving requires rapid handover of responsibility for driving operations from the system to the driver when driving becomes difficult (Table 1).
This chapter presents TDK Group products and technologies that link cars and humans to provide sensory information other than visual.

Figure 1: Example of a digital cockpit
Example of a digital cockpit
Table 1: Autonomous driving levels defined by the Society of Automotive Engineers
Driving Mode SAE Level Driving Operations
Full automation Level 5 ・The system performs all operations (no limitation on areas)
・The system responds even during emergencies and when system operation is difficult
High Automation Level 4 ・The system performs all operations in certain areas (highways, etc.)
・The system responds even during emergencies and when system operation is difficult
Conditional automation Level 3 ・The system performs all operations in certain areas (highways, etc.)
・The driver responds even during emergencies and when system operation is difficult
Partial automation Level 2 ・The system supports both steering and acceleration/deceleration
Driver assistance Level 1 ・The system supports either steering or acceleration/deceleration
No automation Level 0 ・The driver performs all operations

Piezo actuators convey tactile sensations and the feel of operation

If an HMI can be created as a means of conveying not only visual information but also tactile information, it will be possible to enhance the feel of operation when operating devices and the sense of realism when using infotainment functions. TDK's PowerHap™ piezo actuators can provide clear responses to drivers. They can be made thinner than electromagnetic actuators, which makes it possible to embed them in small spaces such as a steering column. In addition, the ultra-thin PiezoHapt™ actuators use various vibration expressions to enhance touch panel functions for more reliable operability. PowerHap™ and PiezoHapt™ piezo actuators have excellent responsiveness, start up rapidly when vibrating, and can create varied vibration patterns to generate tailored sensations. Moreover, they generate voltage when force is applied, so they can be used in conjunction with pressure sensors, which are input devices.
TDK is working with Boréas Technologies Inc. by collaborating on the company's piezo actuator drive ICs to provide solutions that enable developments to faithfully create freely designed tactile patterns.

Table 2: Features of TDK's piezo actuators
  Piezoelectric Electromagnetic
PowerHap™ PiezoHapt™ ERM, LRA
PowerHap™ PiezoHapt™ ERM, LRA
Thickness / mm 1.2 - 2.4 0.3 / 0.35 3
Acceleration [G] / 20g mass 8 - 65 1.6 / 1.5 2 - 5
Rapid start up / ms < 1 < 1 20 - 50
Voltage / V 60 / 120 12 / 24 3
Unrestricted waveform design Yes Yes No
Pressure sensitivity Yes Yes No
Figure 2: Excellent responsiveness even with complex vibration designs
Excellent responsiveness even with complex vibration designs

・Since the actuators are thin, they support flexible designs for all types of devices.
・Rapid start up and unrestricted vibration design
* ERM and LRA support only sine wave design.

MEMS microphone eliminates road noise and enables reliable voice operation

Voice Recognition is a key component in the Digital Cockpit. Equipped with numerous microphones, this will enable the operation of onboard devices, such as the air conditioning, and be used with voice communications. While driving the interior space is filled with various noises such as wind, traffic and the motor itself. To ensure reliable audio capture under these conditions, the use of enhanced performance microphones suitable for noise cancelling and voice capture technology are needed.
TDK's MEMS microphones can fulfill the technological requirements for automobile interior environments. The ICM-40730 features the world's highest S/N ratios at 74dBA, The INMP621 enables easily to realize directional microphone system in automobile interior environments. It is because of the addition of directional algorithm which uses digital interface of pulse density modulated (PDM) linked with two microphones to be time multiplexed on a single data line. The T4078 has an AOP/dBA of 135 great for listening in noisy environments, and the ICS-40300’s low frequency response makes it an excellent choice for precise phase matching.
By incorporating these microphones into various sites in the vehicles interior, it is possible to selectively capture the voice of speakers at specific locations, and to listen and cancel out obtrusive noises, making the Digital Cockpit a key selling point of the vehicle.

Table 3: MEMS microphone lineup
Product Number MMICT4078-00-908 ICS-40730 INMP621 ICS-40300
Product image T4076 ICS-40730 ICS-41351 ICS-40300
Product type Analog output Analog output Digital output Analog output
Dimensions (L x W x T) / mm 3.35 x 2.5 x t:0.98 4.72 x 3.76 x t:3.5 4 x 3 x t:1 4.72 x 3.76 x t:3.5
S/N ratio / dBA 66 74 65 63
AOP / dBA 135 124 133 130

* Please use MEMS microphones after confirming the product operating temperature and using a microphone within its guaranteed range. Contact TDK for details.

Inquiries concerning MEMS Microphones »

Ag-stacked transparent conductive film provides electrical functions to the windows surrounding the vehicle interior

A smart and stylish digital cockpit can be created by adding electrical functions to the front, rear, and side windows and the surfaces of information displays. By adopting TDK's Ag-stacked transparent conductive films, which feature both high transparency and low resistance and are also flexible, we are enabling applications such as light control film (our product used as an electrode) and functional enhancement of glass surfaces to serve for example as touch sensors, antennas, or anti-condensation film heaters (our product used as an element of functional films). The surface resistance is 10Ω/sg., lower than that of ITO, which is widely used as a transparent electrode material. As a result of these outstanding characteristics, the films can contribute to creating practical and attractive vehicle interiors.

Table 4: Ag-stacked film specifications
Structure Type A Type B
Material PET PET
Surface resistance (Ω/sg.) 10 4
Total light transmittance (%) 87 82
Haze (%) 0.5 0.5
b* (Yellow tint) 2.5 5.5
Figure 3: Film structure of TDK's Ag-stacked films
Film structure of TDK's Ag-stacked films

Piezo speakers support unconstrained creation of sound fields in the vehicle interior (under development)

Voice information has advantages not found in visual information as a means of conveying reliable information to the driver and enhancing the sense of being there with infotainment content. TDK's PiezoListen™, the world's first piezo full-range speakers (under development), will create smart and advanced sound systems.
The speakers are slim at just 0.7 mm but feature high power sound output over the wide frequency range from 200 Hz to 10 kHz. They are able, for example to output sound from dashboard speakers or displays, substantially increasing the degree of freedom in speaker placement. In addition, PeizoListen™ is highly directional and can provide uniform sound throughout the vehicle interior. By embedding multiple PiezoListen™ speakers in various locations throughout the vehicle interior, the output of each can be controlled to design sound fields and send sound only to where it is needed.

Figure 4: Speakers can be embedded anywhere in the vehicle interior including the dashboard
Speakers can be embedded anywhere in the vehicle interior including the dashboard
Table 5: <Reference>PiezoListen ™ lineup for general use
Products can be customized for automotive applications. Please inquire regarding customizations.
Product number PHUA2010-049B-00-000 PHUA3015-049B-00-000 PHUA3030-049B-00-000 PHUA6630-076B-00-000
Product image PHUA2010-049B-00-000 PHUA3015-049B-00-000 PHUA3030-049B-00-000 PHUA6630-076B-00-000
Product dimensions (mm) L:20 x W:10 L:30 x W:15 L:30 x W:30 L:66 x W:30
Thickness (mm) t=0.49 t=0.49 t=0.49 t=0.76
Capacitance / μF 1.0 2.3 4.8 7.8