We are gonna discuss the research paper Muscle-Propelled Force Feedback: Bringing Force Feedback to Mobile Devices, by Pedro Lopes and Patrick Baudisch from Hasso Plattner Institute, Postdam, Germany. It is mainly talks about force feedback in gaming experience.
The research talks about the potential of force feedback in Human Computer Interaction, miniaturized the force feedback devices into a mobile version. The research probably is aimed to fellow researchers in Human Computer Interaction particularly to those who interested in haptic feedback from devices. The research also aimed to developers in Human Computer Interacive field and the possibility to give a more haptic feedback in device to be developed. As the experiment is using mobile device based game, the research also may aimed to give gamer who play video game the new experience from playing game by having a force feedback when playing game.
Having a unique and immersive sensation of feedback when playing games can give users pleasant and immersive experience in playing games. There are many ways to give user an extra sensation when using device or playing games, on of them is force feedback to the user. Force feedback has been used to enhance immersion in video games, because it provides physical forces that can counter the users movements, thus provides an extra dimension and sensation to user. There are limitations for this force feedback to be used though, as most force feedback device require physical motor and mechanics, it tends to difficult to miniaturize so it can be fitted and used to a mobile device whilst still maintaining force needed to give the physical forces feedback to user movements. Recent use of haptic feedback in mobile device mostly revolves around vibrotactile feedback to the user. The research wants to push the force feedback in mobile device to give users physical feedback and moves the muscles of the users while playing the games.
As the most force feedback devices involves physical actuators, scaling down the device is not an easy task, especially it is targeting the mobile device. But the approach taken in this research is not taking the way to miniaturize the physical actuator or anything, it is using the user muscle power as the “replacement” for motors. They utilize electrical muslce stimulation to actuate muscle. The utilization of EMS in HCI research has been done previously, especially in other research “PossesedHand”, it is utilizing the EMS to forcefully moves the human muscle by giving electrical stimulation on certain areas.
The main claim of the research is they create concept of creating mobile force feedback using computer-controlled muscle stimulation and force the muscle by. They approach the concept to achieves miniaturization by eliminating mechanical actuators, such as motors, and substantially reducing battery size, as it is two orders of magnitude more energy-efficient to actuate a muscle (which receives its energy from the human body) than to drive a motor. With user studies, they clamied that already verify that the prototype creates sufficient force and that its effect is indeed perceived as force feedback. To gives user’s muscle correct stimulation, the placement of the electrode also need to be considered as the different muscle will gives different movement.
Their theories about EMS in HCI is already researched and discussed by other research papers such as Kruijff et al. manually induced muscle contractions in participants’ biceps while playing videogames on a desktop computer. In the same vein, Farbiz et al. used forearm stimulation to render the sensation of a racket hitting a ball in an augmented reality tennis game. And more recently, Tamaki et al. used EMS to actuate human fingers. The technique targets situations where the user’s input must be mediated or assisted, such as while learning to play a musical instrument. Unlike this assistive approach, this reserach work counters the users’ input, causing it to be perceived as force feedback.
Their approach to optimizing force feedback for size and weight also has been discussed in other research work such as MimicTile, a flexible actuator placed on the side of a mobile phone that can dynamically regulate its stiffness using a shape memory alloy. SqueezeBlock is a programmable spring device that provides force feedback while grasped. InGen is a self-powered wireless rotary input device capable of force feedback. Finally, other approaches produce force momentum (i.e., torque) by mechanically moving a weight around, such as GyroTab and Hemmert et al’s device.
What are they doing is, they build a mobile phone-sized device that induces involuntary muscle contraction by generating a biphasic waveform with a frequency of 25Hz and a pulse width of 290μs. The prototype measures 133mm × 70mm × 20mm and weighs 163g. It is comprised of an arduino nano microcontroller, which communicates via USB or Bluetooth with its host device, here an HTC One X mobile phone. The battery-powered signal generator is coupled to a medically compliant operational amplifier that outputs a maximum current of 50V/100mA over a 500Ω load. Four reed relays allows them to map the signal to up to four channels.
The device is mounted on the back of a mobile phone, and the player has connected it using two skin-electrodes to the palm flexor muscles of each of his forearms. The device renders the winds by trying to tilt the device against the user’s will. It achieves this by stimulating muscle tissue in the user’s arm though the electrodes, triggering an involuntary contraction. This causes the user’s arms to tilt sideways and thus the device to tilt. Since the airplane is controlled by tilt, the involuntary tilting threatens to derail the airplane. To stay on course, players counter the actuation using the force of their other arm.
They tested the device to the participants and measure the generated force and investigated how the participants perceives the force feedback generated by the device by played the games and wear their device and compared it with vibrotactile feedback. Their experiments shows that alll subjects expressed to prefer force feedback to vibrotactile feedback. Furthermore, participants’ opinion suggested that force feedback contributed to a positive gaming experience.
Having a forced physical feedback stimulated by electrical currents into our muscle sounds scary but actually it gives the gamer a more immersive experience and we, human, tends to perceive it as a fun experience because the device are designed to give feedback while playing games, which is fun. We need more experiments of force feedback to a more less fun activity, I mean, non-game application.