Principles of operation and the state-of-the-art a 'novel' sensor/actuator technology

Abstract

Sensors and actuators have been around for a long time. Their use was undervalued at some point in time but nowadays they found their way in practically everything. One of the main things would be game controllers which is as popular as mobile phones. With the advent in technological advances, extreme competition in the gaming industry keeps brings new innovative and simple ideas for its users. From the simple, bulky joystick to the sleek, simple to use Wiimote, sensors and actuators has shown their potentials. And yet to come is the new “headband”, controlling your persona in the game using your brain directly is the new killer. This article takes you from simple to very complicated designs as to where sensors are being used in the gaming industry.

Introduction

A sensor is a device that detects or measure a physical quantity. The opposite device is an actuator which converts a signal (usually electrical) to some action usually mechanical. A transducer is a device that converts energy from one form into another. Actuators and sensors are therefore forms of transducers. [1] Actuators and sensors are used in our everyday life. They have innumerable applications such as piezoelectric devices, motors and relays. These are examples of actuators and sensors used in control systems. Actuators and sensors may be used in a control system in several ways listed below:

Sensors and actuators in computer controlled systems continually monitor the operating condition of many devices in today’s world. Through the sensors, computers receive vital information about a number of conditions, allowing minor adjustments to be made more quickly and accurately than mechanical systems. Sensors convert temperature pressure, speed, position and other data into digital or analog electrical signal.
A digital signal is a voltage signal that is either on or off with nothing in between. A switch is the simple types of digital signal sensor. Digital signals are the easiest for the computer to understand because it reads the signal as either on or off.
This article looks at the use of actuators and sensor technology as one of the latest and state-of-the-art technology such as used in video game console, such as Nintendo Wii. Video and computer games controls and controllers have developed at an exponential rate in the last decade. The introduction of new and more immersive control technologies such as motion sensing and touch screens into the commercial games market has enormously changed the design of games and is on the way to change more. The video and computer game industry is one of the largest entertainment industries in the world. [3] Conventionally, games were either run on a PC or a simulated program or an externally controlled device inputting to a specialized video system. [4] Nowadays, games come in all shapes and sizes. They all have a range of different controllers; from single handed controllers, analog controllers, digital controllers, steering wheels input and much more. All these have been developed in order to satisfy the user’s needs for control, comfortable use, quick and accurate response and ease of function access. [4] Taking Nintendo Wii as the first example, the Wii Remote which is also known as the Wiimote will be the focus. The Wiimote made itself apart from more conventional games controllers in the sense that it senses position, relative to an infrared sensor bar and acceleration more distinctly an accelerometer. [5] The Wiimote is a consumer gaming product that allows users to interact with the Nintendo games displayed on a television screen by moving and pointing. Players can imitate shots in golf and tennis and use the Wiimote as a steering wheel to control an off-road vehicle animated on the screen. The wireless remote controller contains motion sensors that detect rotational and translational acceleration, allowing the user to make the appropriate movements for the game in the play, rather than communicating by pressing buttons. It transmits the motion measurement to the Wii control console using Bluetooth technology. [6] The main working principles lie inside the controllers. Its main feature is the motion sensing capability which allows the user to interact with and manipulate items on screen via movement and pointing through the use of accelerometer and optical sensor technology. [7] The Wiimote’s main components are Bluetooth, accelerometers, buttons, speaker, memory and are I2C master. [8] The Wiimote has the ability to sense acceleration along three axes through the use of an accelerometer. An accelerometer is an electromechanical device which measures acceleration forces. The measurement of acceleration is used as an input into some types of control systems which in turn uses the information to correct for changing dynamic conditions. It has the ability of sensors to detect, collect and calculate environmental data. Figure 2 shows a 3 axis accelerometer circuit board.
Modern accelerometers are also known as Micro Electro- Mechanical System (MEMS) device. MEMS accelerometers detect and measure motion, vibration, rotational spinning and gravitational acceleration. MEMS had been recently introduced in the design of laptops to prevent and detect damage in the event of the laptop being dropped. Its main component is a seismic accelerator and some circuitry. [11] The Wiimote uses an ADXL330 accelerometer. ADXL330 is a small, thin, low power complete 3-axis accelerometer with signal conditioned voltage outputs. ADXL330 measures the acceleration with a minimum full scale range of ±3g. It measures the static acceleration of gravity in tilt-sensing applications as well as dynamic acceleration resulting from motion, shock or vibration. [9] Figure 3 below shows a block diagram of the ADXL330 accelerometer as in use in the Wiimote.
The ADXL330 uses a single structure for sensing the 3-axes. As a result, the three axes sense directions are highly orthogonal with little cross axis sensitivity. Rather than using additional temperature compensation circuitry, innovative design techniques ensure high performance is built-in to the ADXL330. [12]

Accelerometer Systems

For sensing the quantities of acceleration, velocity and distance travelled, systems based on accelerometers are used. The basis of all accelerometers is the action of acceleration on a mass to produce force, following the equation F=Ma where F is the force measured in Newton, M is the mass in kilograms and a is the acceleration in m/s2. The use of a mass, which is often termed as inertial mass, in this way is complicated by the effect of the acceleration of gravity which causes any mass to exert a force that is directed towards the centre of the Earth. The mass that is used as part of an acceleration sensor must therefore be supported in the vertical plane, and the type of support that is used will depend on whether the accelerations in this plane are to be measured. [2]

Principle of the three-axis acceleromter

The basic operation principle of the three-axis accelerometer is shown in the Figure 4 below.
Figure 4 consists of four independent single-axis sensing elements, each with its most sensitive axis inclined to the chip surface at an angle α. The output signals form the four sensing elements depend on the acceleration according to: [14] Si(f) denotes the sensitivity of element number i and ax, ay and az which represents the accelerations in the x, y and z directions.
It is assumed that all the sensing elements have similar sensitivities, therefore Si =S and the same applied to the inclination angles resulting in the following equations for the extraction of x, y and z axis accelerations: [14] Detailed analysis of the accelerometer response is available in Ref. [14] Nintendo Wii does not only have sensors to allow users to effortlessly control the game but they also have actuators to make them feel more in control. An example of actuators in Nintendo Wiimote is the vibration motor. The vibration motor is an actuator which is widely used in haptic (touching sense) interactions and gaming. The vibration motor creates vibrotactile stimulation for haptic interaction both in commercial products such as mobile phones, gaming pads and in research equipments for virtual reality and human computer interactions. The motor has the advantage of being small, inexpensive and capable of inducing loud vibrations compared to other types of vibration actuators. The same technology is in use in Xbox 360 and Sony Playstation 3. [15] Such interactions allow the user to feel more in control of their game.
Dual Shock 3 is the latest controller which is capable of providing feedback based on reaction from onscreen or vibration function. The controller incorporates features and wireless design of the Sixaxis wireless controller with rumble capabilities. [16] The Sixaxis wireless controller (Figure5) is the official controller for Sony PS3. It operates using Bluetooth technology. The main feature with this controller is its ability to sense both rotational orientation and translational acceleration along all three dimensional axes which provides six degrees of freedom. [17] With extreme competition in the world of video gaming, progress is being outdated within months of discovery. Some players have even been turning to drugs to try to improve their performances. [18] Meanwhile OCZ Technology Group Inc. has been working on their latest video game control and came up with the Neural Impulse Actuator (NIA). It is the world’s first gaming control system that forgoes tactile inputs in favour of inputs from muscle movement, brain waves and glance (eye movement) levels. [18] The system is calibrated to deal with the individual user physiology. The main component of the NIA is a headband. Once the user put the headband on at temple level, the GUI (graphical user interface) appears which allow the user to calibrate each input, which is the muscle movement, brain waves and glandular levels. [15] Once calibrated the NIA was put to test by OCZ VP of Technology Department, Dr. Michael Schuette. The latter used the mouse only for pointing, and using only his mind and facial muscles, he ran through the game like what the DailyTech described as “a hot knife through butter.” [18] Figure 6 below shows the demonstration of the Neural Impulse Actuator.
The concept behind the headband is fairly simple. It holds 3 sensors which read electrical impulses in various frequency ranges which equate to a number of different facial movements.[19] The signals are then transmitted to an interface unit where they are amplified, digitized and decoded to produce multiple command signals that users can learn to modulate consciously to control the games. It is possible to use this system to achieve multiple functions.[19] The headband has the ability to differentiate between a range of actions including facial muscle contraction, side to side eye movements and alpha and beta brainwave fluctuations. Figure 7 below shows a sample screen of the Neural Impulse Actuator. [19] Neural Impulse Actuator is not the only new gadget in the field. One of the most recent update is from The Guardian, February 2008 under their Technology News and Features section. It has been reported that at the Consumer Electronics Show in Las Vegas, there was a man waving his arms at a screen with a giant grey cube on it. He was wearing a headset lined with brainwave-reading sensors. Marco Della Torre is the product engineer at Emotiv, a San Fransisco-based company behind this prototype neurofeedback game. Figure 8 below shows the demonstration of the game. [20] The game uses sense and sensor ability. The game is hooked up to the pattern of the user’s brainwaves. Emotiv is just one of the players in this competition. Just like OCZ and Emotiv, NeuroSky also develops the same type of technology. In the case of NeuroSky, a single-sensor headset scans the brain for levels of focus, anxiety and meditative state. [20] Not only that game players train to compete against each other, now with the new neural impulse actuator, learning as to how to control the brain rhythms would be put to good use. A study was conducted to investigate the ability of subjects to manipulate sensorimotor mu rhythm in the context of a rich visual representation of the feedback signal. [21] In late 2006, a unique wireless motion sensor system named Fusion was developed. This technology’s main function was the system’s main ability to imitate any other motion-based controller. It allowed games designed specifically for Nintendo Wii motion controller to be used in any other format. Unlike the Wiimote, the Fusion system does not require the user to point the product at a screen nor does it have movement limitations. It is a combination of ultrasonic and RF technology with 3-axis accelerometers. The technology is one that can be integrated into any input device. [22] Not only that games have been overtaking this decade, sensors have even found their way into Nike shoes and it is connected to an iPod sensor. It all started the same way cell phones work; communication between the sensor in the runner’s shoes and the iPod uses radio waves. The sensor in the shoes detects every step the runner made and this information is transmitted to the receiver which sent it to the iPod Nano. It is then relayed to the user via headphones or visually displayed on the screen of the iPod.
The sensor in the shoes has a piezoelectric accelerometer. As discussed before accelerometers measures the acceleration at which the runner will be running in this case. Piezoelectric materials produce electrical current when they change shape. A piezoelectric sensor uses quartz, silicon or crystals to produce the electricity when deformation occurs. Figure 8 shows a piezoelectric sensor that has motion sensing capability used in Play Station 3 Controller. [23] The crystals are very small and depending on how the crystals are cut, they produce electrical charge when compressed along a specific direction or plane. This allows the piezoelectric sensor to be very small and accurate. It also has motion sensing capabilities which is used in Playstation 3 and Nintendo Wii. [23] A device that has developed in the early millennium is the MobZombies. MobZombies is an electronic game whereby the player’s physical body movement control their persona in the game. In the game, the player’s role is chased by a mob of zombies that must be evaded in order to survive. The player must run and turn in order to control their avatar’s forward movement and turning movement. Through the use of a wearable sensor, the player’s running and turning are translated into the persona’s movement. Three different types of wearable sensor design were investigated. [24] The first design of the sensor framework used a handheld GPS device. The second sensor framework used a digital magnetic compassand tri-axis accelerometer.
The third sensor framework used a MEMS integrated two-axis micro-mechanical gyroscope and tri-axis accelerometer. The accelerometers are used in the same way described above for the Wiimote. [25] The MEMS gyroscope is also known as vibratory gyroscopes. Vibratory gyroscopes were demonstrated in the early 80’s. A typical example of the technology at that time was the quartz tuning forks like the Quartz Rate Sensor by Systron Donner. But it was only in the year 1991 that the first batch of silicon microcachined rate gyroscopes was demonstrated. Gyroscopes are classified in three different categories; namely, inertial grade, tactical-grade and rate-grade devices. Coming back to the Wearable sensor, the gyroscope used in the second design was a vibrating-wheel gyroscope. The latter has a wheel that is driven to vibrate about its axis of symmetry and rotation about either in-plane axis which results in the wheels tilting. It is possible to sense two axes of rotation with a single vibrating wheel. [26] Pirates is another game that uses sensors. Unlike Nintendo Wii, Playstation 3 and Xbox 360, Pirates does not require the physical presence of various players. The game interface is designed to make use of the stylus and any interaction is made by tapping on the screen with the stylus. Because the game is mobile, the players are required to walk around with the device in their hands. On the handheld devices, the game is represented by a graphical interface accompanied by sound effects to highlight the transitions between game events. To determine the physical whereabouts of players in the game, proximity sensors are in-built to tag physical location and the handheld devices. All the proximity sensors which are RF based act as beacons, transmitting a unique ID code. All the proximity sensors also “listen” for RF activity in their immediate surroundings. When a sensor mounted on a handheld device detects a signal from another device a notification is sent to the game engine via the WLAN. The proximity sensors are based in the TR1001 RF transceiver from RF Monolithics, with low-level control using an Atmel AT89C4051 microcrontroller and an RS-232 voltage level converter for interfacing with the serial port of a handheld device. The conclusion from that particular study showed that the sensors allow the programmers to determine the player’s position relative to one another and to locations. [25] Wireless sensor network is another type of sensor used in the games industry. It offers the opportunity to introduce different kinds of physical data into mobile pet games. Wireless sensor networks consist of many small, low cost, spatially dispersed, communicating nodes, which has also been recently proposed for application such as public safety, medical, environmental, surveillance, home and office security and transportation. With the trend in increasing used of integrated electronics, such as performance to cost ratios, low power radios and micro-electro-mechanical systems (MEMS) sensors, it now allows the construction of sensor nodes with signal processing, wireless communications, power sources and synchronization into inexpensive miniature devices. Sensor nodes function much like individual ants that, when formed into a network cooperatively accomplish complex tasks and provide capabilities greater than the sum of the individual parts. [27] Figure 11 shows the sensor nodes in the wireless sensor network. They are classified in two categories namely, sensor and sink node. The sensor node is the majority of nodes which is also inexpensive and has simple functions. [27] How all this link to the mobile pet game is another story which is shown in Figure 12?
As illustrated above, the users will deploy several sensor nodes in their house and each sensor node corresponds to a particular virtual pet. These sensor nodes make up a wireless network connected with the internet through a home gateway which is considered as a sink node in wireless sensor networks. The handle mobile device is connected to the internet via packet access network and visits the pet game server or interacts with wireless sensor networks via pet game server. The whole architecture is composed of four entities sensor node, home gateway, handle mobile device and pet game server. [27] This study showed a new architecture for the integrating of sensor network into mobile pet game. This architecture can effectively integrate multiple small scale sensor networks with mobile terminals and pet game server. [27] Actuators and sensors as we have seen till now walk more or less hand in hand. We have spoken earlier about haptic sensors for more tactile sensation. The following is a review of a patent by Moore, filed in 2000, on “Actuator for providing tactile sensations and device for directional tactile sensations”.
The invention relates to interface devices that will allow humans to interface with computer systems and more particularly to computer interface devices that allow the user to provide input to computer systems and allow computer systems to provide haptic feedback to the user. [28], [29], [30] Just like the user usually interact with interfaces on a computer using Graphical User Interfaces, other devices such as, mouse, joystick, trackball, steering wheel, stylus, tablet, pressure sensitive sphere are examples of human computer interface devices, typically this is another interface but for more haptic feedback. In some interface devices as seen earlier, force feedback or tactile feedback is also provided to the user, more generally knows herein as “haptic feedback”. These types of interface devices can provide physical sensations which are felt by the user. One or more motors or other actuators are coupled to the joystick, mouse or other device and are connected to the controlling computer system. In force feedback system, the computer system controls forces on the movement of the joystick or mouse in conjunction and coordinated by displayed events and interactions by sending control signals to the actuators. This invention was directed toward providing a low cost actuator and directional haptic feedback for a haptic feedback interface device. [28], [29], [30]

Conclusion

The gaming industry has revolutionized with the advent of sensors and actuators. The more development actuators and sensors went through, the more innovative and simple was the result for their use for general users. From the joystick to neural impulse actuator as controllers, sensors and actuators showed they use in everyday life. From the simple, bulky joystick to the sleek, simple to use Wiimote, sensors and actuators has shown their potentials. And yet to come is the new “headband”, controlling your persona in the game using your brain directly is the new killer. There are still many other types which are being developed for ease of use for the player. The players need is what gets this industry moving at a very fast pace. Sensors and actuators have reached their peak and are still continuing to astound us, users and will continue to do so as long as the need is there. [31, 32, 33]