Sunday, April 21, 2024

Developing Haptic Systems

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Haptic technology is a unique form of mechatronics, encompassing mechanical, electrical, and computational elements. With sophisticated sensors and actuators, it offers users a more enhanced interaction with machines than current conventional systems. Haptics provides users with visual and auditory cues from computer and tactile experiences like touch, pressure, weight, texture, and warmth. This fosters a more profound, tangible connection with our devices, elevating our engagement with applications to a more immersive level. In this blog, we will explore how implementing haptics benefits a wide range of diverse applications as well as the latest design techniques in haptics feedback.

Haptic Use Cases

Let’s begin by taking a look at current and future implementations of haptics and consider why we need or want haptic technology.

Medical

In the medical field, enabling doctors to feel what a robotic hand touches, for example, permits greater control and safety. Surgical techniques like laparoscopic surgery that utilize haptic technology allow surgeons to make smaller incisions that heal more quickly for the patient. Using remote-controlled manipulators coupled with video, a surgeon can perform delicate operations with finer precision than ever before. A surgeon must know how much force a scalpel is applying. Too much, and the incision is too deep. Too little, and the incision is too shallow. By the same token, a surgeon needs to know if they are moving a blood vessel out of the way or tearing through it. Here is where force feedback is essential.

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Gaming

In gaming applications, instead of joysticks and keyboard clicks, haptics provides virtual feedback to the user that resists control force, also allowing the user to feel the sensation of textures and other physical phenomena. So far, micromotors, piezo actuators, fluidic transfers, and air pressure are being used to physically interact with a user. However, developing with these haptic technologies is much different than developing other, more traditional machine designs.

Fortunately, device makers are addressing these needs with development systems and application examples to help guide engineers who are new to haptic technology. One key technology used in haptic designs is accelerometers. These are used in headsets to control the field of view, gloves to monitor hand motion, and remote robotic assemblies to provide force feedback information.

Many device makers offer accelerometers for OEM applications and development kits, application notes, and reference designs. What’s more, because of the widespread adoption of accelerometers in cell phones, these multi-axis devices are low-cost and readily available from standard distributors and manufacturers. A typical accelerometer development kit contains multi-axis sensors and a computer interface like USB, I2C, SPI, or UART. Outputs can be digital or analog, and measurements up to 16G are not uncommon.

Consumer Devices

For applications that require complex motion capture and processing, haptic designs are increasingly implementing Inertial Measurement Units (IMUs). IMUs are essentially an accelerometer + gyroscopes + magnetometer sensors. These highly integrated, ultra-low-power sensors can be customized for a range of high-performance applications, including wearable devices, head-mounted devices, smartphones, cameras, drones, and AR/VR/MR headsets. With ready-to-use software algorithms, IMUs make for a robust smart sensor system package capable of easily calculating orientation, position, and velocity, which can be used for position tracking and activity/gesture detection with high precision and low latency.

Furthermore, due to economies of scale and widespread adoption of IMUs in smart phones, cameras, drones, and other consumer devices, these multi-axis programable smart sensor systems are also low-cost and readily available from standard distributors and manufacturers. Just like accelerometers, typical IMU development kits include a multi-axis sensor, environmental sensors, and a computer interface like USB, I2C, SPI, or UART.

Haptic Design Techniques

With such a variety of applications for haptic technology comes the emergence of several design techniques that engineers continue to hone and develop. Some haptic designs use microfluidic techniques that pump fluids into and out of an array of chambers and are also viable for creating sensation on the skin. In most cases, micromotor-based pumps, microvalves, and capillary tubes are used. Fortunately, motor control technology is mature, and many motor control development kits are readily available to help enable these microfluidic techniques.

Op-Amp and Microcontroller Designs

Micromotors do not draw large amounts of current and can be typically powered using Op-Amps to drive the motors bidirectionally. In applications where Op-Amps alone are not enough to drive the micromotors, microcontrollers with motor control capabilities like higher current drivers, pulse width modulation (PWMs), multiple timers, and even analog outputs can be employed to drive the many motors, pumps, or micro-valves.

Digital Signal Processing

Processors with digital signal processing (DSP) capabilities are especially useful for driving micromotors and monitoring back EMF, which can be used to measure resistance to digitally asserted pressures. Example development boards include a processor section and a power transistor array, if needed. Haptic designs that employ DSPs offer tremendous potential for delivering immersive experiences for games, movies, music, and more. By supplementing audiovisual content with tactile vibrations, haptic designs can enhance sensory stimulation and increase user engagement. Processors with DSP capabilities can perform complex filtering algorithms for precision motor control of multiple motors in the application. Moreover, these motor control techniques can also be used to create air pressure-based sensation systems and fluid pump-based systems. In addition, this technology can be adapted to drive micro piezo actuators that can provide electromechanical sensation or may also drive ultrasonic emitters and piezo actuators.

Ultrasound Haptics

There is also a clever haptic technology design that employs ultrasonic waves from an ultrasonic array that merges to produce a perceived force. This type of ultrasound haptic technology creates mid-air haptic sensations using focused ultrasound waves, so people can experience haptic feedback against the hands without any physical contact with a device. While it has primarily been utilized to give tactile feedback, like the sensation of pressing a virtual button, its application is expanding to stimulate and affect larger areas of the body.

The next-generation of high-definition (HD) haptics will require more than hardware alone. Incorporating software into future haptic system designs will be critical for overcoming the limitations of hardware-only solutions.

Conclusion

Haptic design is a relatively new discipline, but there are development tools and guidance out there for engineers. As haptic products emerge, more development kits and application notes will emerge. While medical, industrial, robotic control, and remote repair may be developing critical use haptic technology, the gaming industry will push this technology along faster and further. Readily available higher volume applications will drive haptic technology to make specialty applications easier to design, creating possibilities for future innovations and uses.


After completing his studies in electrical engineering, Jon Gabay has worked with defense, commercial, industrial, consumer, energy, and medical companies as a design engineer, firmware coder, system designer, research scientist, and product developer. As an alternative energy researcher and inventor, he has been involved with automation technology since he founded and ran Dedicated Devices Corp. up until 2004. Since then, he has been doing research and development, writing articles, and developing technologies for next-generation engineers and students.

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