Design of Haptic Interface for Brickout Game

Wanjoo Park, Laehyun Kim, Hyunchul Cho, and Sehyung Park Intelligence & Interaction Research Center

Korea Institute of Science and Technology, Seoul, Korea { wanjoo, laehyunk, hccho, and sehyung }@kist.re.kr

Abstract— This paper introduces a haptic interface for brick games. Conventionally the game user uses mouse or keyboard to play the brick game. However, these input devices do not provide intuitive interface for the game and any tactile feedback to the user. We use a haptic dial to add tactile feedback to enhance game effects in addition to visual and sound effects. The user changes the position of the paddle by spinning the dial knob and feels various tactile feedbacks according to the game context. Tactile feedbacks include friction, jog dial, barrier, detent, and any combinations of these effects which are programmed based on the amount, frequency, and direction of torque along the rotational path. These effects are used as either penalties or useful tools. The proposed haptic dial interface makes the game more fun and gives a very intuitive interface to the game user.

Keywords- haptic interface; brickout game; dial knob;tactile feedback

I. INTRODUCTION Haptic interface that has recently emerged allows the user

to feel tactile feedback via the sense of touch. It includes force/torque feedback, pressure, vibration, heat, and even pain. This technology can be used in various applications such as medical simulation [1], mobile phone, automobile, and game. Especially, the success of the Wii [2] and the haptic phone [3] providing tactile feedback leads to integrate haptic interface into game devices. Most of game devices with tactile feedback such as Wii, PSP, and Nintendo DS give simple vibration effects to the user. PC-based video games work with mouse, keyboard, and joystick without tactile feedback.

Over the past few years, several studies have been made on tactile feedback controller. Karon E. introduced a variety of haptic devices and design parameters [4-5]. The related research to apply games using haptic effect includes Yuichiro’s work. He proposed a device that gives a user feeling as if virtual object is inside the device when shaking it using accelerators and actuators [7]. Another research is Jukka’s work. He developed the bouncing ball game using accelerator sensors and tactile feedback actuators [8].

There are related works for the 1 DOF (Degree of Freedom) dial knob. Scott S introduced various haptic devices and haptic rendering methods [9]. And this programmable tactile feedback was applied to vehicular instrument controls and multimodal prototyping in the early phase of the product development [10-12]. El Saddik defined the Collaborative

Haptic Audio Visual Environment(C-HAVE) and proposed the future potential of haptics [13].

This paper introduces a brickout game incorporating haptic feedback. This game is popular for children and the elderly since it is very simple and easy to learn. They need the simple game because of late physical response. In addition, the tactile feedback may stimulate their brains through the sensory organs. We will do research about the brain response of haptic effects for children and the elderly in future.

The main objective of the brickout game is to remove all the bricks from the wall by hitting them with the ball (Fig. 1). The user can move the paddle left and right by spinning the dial knob and try to make the ball bounce off the top and side of the wall. Some of bricks are connected to a specific haptic effect. When the ball hits a specific brick, the user feels the programmed tactile feedback through the haptic dial. These tactile feedbacks can make the game easier or more difficult.

We designed various tactile feedback effects which are defined by torque profiles along the angular position. The tactile feedback includes friction, jog dial, barrier, multi-step detent, detent gradation, and a combination of these effects. These haptic effects make the brickout game more fun and the dial knob give an intuitive interface to move the paddle position.

Section 2 describes hardware system of the haptic dial interface and section 3 explains implementation of haptic effects. Implementation of a brickout game based on the proposed system is described in section 4, followed by the conclusion in section 5.

Fig. 1 Brickout Game GUI

Paddle

Ball

Bricks

978-1-4244-4218-8/09/$25.00 ©2009 IEEE

II. HAPTIC DIAL HARDWARE In this section, we explain the detail hardware configuration

for haptic dial knob. The block diagram of the system is shown in Fig.2 and the prototype of the device is shown in Fig. 3.

Fig. 2 Block diagram of the System

Fig. 3 Prototype Implementation of the System

The main processor is the AVR ATMEGA-128 processor and the DAC (Digital to Analog Convertor) is DAC0800 from National Semiconductor. DC motor is used to generate various haptic patterns. We use RE25 with a gear box of 5:1 ratio from Maxon motor. The motor works with 24V/0.6A and 28.8mNm torque. The Dial knob is installed on the motor gear box and allows the user to rotate the knob and feel haptic effects which are programmed along the angular position. The Encoder to measure the angular position is MR 128 with 1000 pulse per turn from Maxon motor. The encoder counter is LS7166 by

LSI computer systems. It is 24bits quadrature counter and DC to 25MHz count frequency. Touch LCD Module (is EZ-TFT350T by Alls Technology) is used to display visual information and to allow touch input. It displays 3.5 inch QVGA 320 x 240 pixels with 24bits true color.

When user rotates the dial, the encoder generates the pulses. Then encoder counter IC counts pulses and the AVR processor read the encoder value. The processor calculates the angle and drives the motor to generate haptic dial effects described in section 3. The user feels the programmed tactile feedback effects according to the game context.

III. HAPTIC DIAL EFFECTS We will begin our discussion by considering the haptic dial

effects for brickout game. These effects are organized by angle, time, location and movement.

A. Angle based Effects

Fig. 4 shows 3 types of angle based effects - Detent Gradation, 3 Step Detents and Jog Dial. Eq. (1) shows the angle based effect which is designed by sine function.

)sin()( θθ θ ⋅= bAfd (1) where, Aθ is the amplitude variable, b is the notch number

per turn, θ is the angle of dial

The detent gradation has notch at regular intervals, period of 2π. The force tailed away gradually as angle is increased. In the case -180° ≤ θ < 0°, Aθ is θ / 2 and in the case 0° ≤ θ ≤ 180°, Aθ is (2π - θ) / θ. Fig. 4 (a) shows the detent gradation effect.

The second effect is the 3 step detents. Fig. 4 (b) shows that it has different amplitudes and frequencies. Around zero degree, it has small amplitude and high frequency but near 180 degree and -180 degree, it has large amplitude and low frequency.

The last one of angle based effects is the jog dial. Eq. (2) and Fig. 4 (c) shows that it is combination of 2nd order equation and sine function. This effect makes the dial location to the position of zero degree. When dial is rotated both CW and CCW by a user, backward toque obstructs a dial rotation. The more the backward toque is increased, the more the dial is rotated.

)1805(,5.0)1805(

)55(),12360sin(

)5180(,5.0)1805()(

2

2

°≤≤°+−=

°<<°−=

°−≤≤°−−−−=

xx

x

xf j

θ

θ

πθθ

(2)

where, θ is the angle of dial

Touch LCD Module

Motor

Encoder

Dial Knob Motor

Controller

Coin

-180 -90 0 90 180

-10

-5

0

5

10

Angle

Tor

que

(a) Detent Gradation

-180 -90 0 90 180

-10

-5

0

5

10

Angle

Tor

que

(b) 3 Step Detents

-180 -90 0 90 180

-10

-5

0

5

10

Angle

Tor

que

(c) Jog Dial

Fig. 4 Torque function graph of angle based haptic effects

B. Time based Effects

Eq. (3) and Fig. 5 express the vibration function in time based effects. We designed tiny vibration and item vibration. The tiny vibration has small At and high frequency (large s) which the item vibration has large At and low frequency (small s).

)2sin()( tsAtf vv ⋅⋅= π (3) where, At is the amplitude constant, s is the frequency

scaling constant, t is a time

0 50 100-10

-5

0

5

10

Time [ms]

Tor

que

0 500 1000-10

-5

0

5

10

Time [ms]

Tor

que

(a) Tiny Vibration (b) Item Vibration

Fig. 5 Torque function graph of time based haptic effects

-180 -90 0 90 180-10

-5

0

5

10

Angle

Tor

que

Fig. 6 Torque function graph of location based haptic

effects

C. Location based Effects

The Barrier is the location based effect. This effect blocks the dial rotation on 180° and -180°. And when dial’s position is near 180° and -180°, it pushes the dial to end point. It is edge effect and its feeling is like a magnet effect. Fig. 6 shows the barrier effect and edge effect.

D. Movemet based Effect

An example of movement based effect is the friction. We simulate it based on the friction con model [14]. The friction toque can be calculated as follow:

)()(

)()(

)()(

)()(

))()(()(

))1()(()1()(

min_min_

max_max_

_

_

_

nPnTelse

TnTthenTnPifelse

TnTthenTnPif

nPnP

LnPnPnP

SnPnPnPnP

difff

fffdiff

fffdiff

fcurrprev

ffcurrnowdiff

fprenowprevfcurr

=

=<

=>

=

⋅−=

⋅−−+−=

(4)

where Pcurr_f is the current position, Pnow is the angular position of the dial knob, Ppre is the previous position, Sf is the scaling factor, Pdiff is the difference of position, Lf is the friction level, Tf is the friction torque.

IV. HAPITC BRICKOUT GAME Fig. 7 shows the brickout game we implemented. We

designed that blue bricks are general bricks and orange ones contain haptic items. The game ball bounces off top or side of the wall depending on collision condition between the ball and the paddle. When the ball hits an orange brick, the brick falls down. If the user catches the brick by moving the paddle and he/she feels a programmed tactile effect for a few seconds. The force gauge on the right side indicates the motor’s torque. The friction gauge shows the friction level of rotational movement.

Fig. 7 Implementation of a brickout game

The haptic dial interface is connected to a PC on which the

brickout game is running through USB interface. The tactile effects are displayed on the LCD in the haptic dial interface in Fig. 7.

The effect of which the user feels now is shown in the center among 6 type haptic effects - Vibration, Friction Up, Friction Down, Barrier, Detent and Slow. This picture shows that the vibration effect is working now.

We describe the haptic effects in more detail in the breakout game. Some of haptic items work as penalties which make the paddle movement more difficult. Some of them work as tools to make it easier.

For Detent Gradation item, the user has a hard time to control the dial around the center point where the amount of the torque becomes the maximum. On the other hands, it is easy to the user to control the dial as the paddle moves far from the center.

The angle based haptic effect like 3 Step Detents provides several different torques and intervals along the angular position of the dial. When the user gets the Jog Dial effect, the dial tends to go back to the center automatically and make the paddle control easier and faster. However, if the user wants to wait the ball on the side zone, he/she has to try to resist the torque to keep the current position.

The vibration is the time based haptic effect. When the paddle collides with the ball, the dial is vibrated by this function with small Av in Eq. (3). At this effect, user is able to feel the collision impact between the paddle and the ball. In addition to the collision effect, vibration function with big Av value in Eq. (3) works as obstacles to control the dial. When the user gets it, he/she has a hard time to control due to the vibration during a few times.

The friction is the movement based effect. The friction of dial is determined by Lf in Eq. (4). To add fun to the game, one item makes Lf zero then user control the dial easily. However another item makes Lf high so that the user feels difficulty to control the dial.

Finally, the Barrier and Edge effect belong to the location based haptic effects. The Barrier is useful to limit the range of the paddle movement. It can be used for either penalty or game tool. When the paddle meets the barrier point, the user can feel the hard stop using strong torque feedback. And when the paddle hits the side wall, the haptic effect makes the dial move toward the wall automatically. The Edge effect is helpful for the user to recognize the wall.

V. CONCLUSION In this paper, we implement a haptic dial interface and

haptic effects for a brickout game. The conventional game devices such as Wii and PSP provide simple effects like vibration. However the haptic effects proposed in this paper are active and various tactile effects. We designed several different tactile effects which have different amplitude, direction, and frequency of the torque along the angular position. They include friction, jog dial, detent, barrier, and any combinations of these effects. The barrier effect can block the movement of the dial at specific points and the detent effect provides a variety of clicking feeling. Other examples are jog dial and edge effect that draw the dial to the center point and the side wall respectively. These haptic effects can be used as penalties or useful tools and make the game more fun. In addition, the dial knob gives a very intuitive interface to change the position of the paddle in the brickout game compared with conventional input devices such as keyboard, button, and mouse.

VI. FUTHER WORK

Through a user study, we will compare the ordinary dial control and haptic dial control in terms of performance and fun while the user plays the brickout game. In addition, we will study the influence of the tactile stimulation to the brain activation via the sense of touch. The haptic dial interface can be applied to other games like shooting games and golf simulation game in which the user need to control the force/torque.

ACKNOWLEDGMENT This work has been supported partially by Tangible

Interaction Technology Project in Korea Institute of Science and Technology.

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