The present invention relates to a novel touch-sensitive input device, like for example input devices commonly designated ‘touchpads’, and that can be used in the computing field as pointing device or for manipulating objects in a virtual environment. This novel touch-sensitive input device is more particularly, but not only, suitable for portable electronic devices, such as for example laptop computers and handheld electronic devices (PDA, mobile phone, handheld pen tablet, etc . . . )
Input devices can be classified in three classes (isotonic, isometric and elastic) as defined in publication: Zhai, S. Human Performance in Six Degree of Freedom Input Control. PhD thesis, University of Toronto, 1995. Isotonic devices are free-moving and use position for input. Isometric devices do not perceptibly move and use force for input. In between isotonic and isometric devices are elastic devices, where resistance increases with displacement. Elastic devices can use either position or force for input.
With any class of input device, there are different ways to map to output, the two most popular being position control (zero-order mapping function) and rate control (first-order mapping function). Zhai found that isotonic devices are better suited to position control whereas isometric and elastic devices should use rate control. The latter require a self-centering mechanism—a way for the device to return to a neutral rate control state—that is difficult to achieve with isotonic devices. Rate control maps input to a velocity vector and moves the display pointer in that direction and speed. Position control maps device input to an output position.
Absolute position control assigns a unique output position to every input position [Buxton, W. Lexical and Pragmatic Considerations of Input Structures. Comp. Graphics, 17,1 (1983), 31-37 & Card, S. K., Mackinlay, J. D., and Robertson, G. G. A morphological analysis of the design space of input devices. ACM Trans. Inf. Syst., 9, 2 (1991), 99-122]. This is typically done when the input and output spaces are coincident, like on a pen-input display.
Relative position control uses a displacement vector from an initial input position to the current input position. The current output position is calculated with the vector and a corresponding initial output position. The definition of this initial input position is achieved by clutching, where the input stream is suspended as the device is repositioned at a new initial input position.
A mapping function uses Control Display Gain (CD gain) to scale the relative displacement vector. Jellinek et al. [Jellinek, H. and Card, S. Powermice and user performance In. Proc. of CHI'90, 1990, pp. 213-220], Accot et al. [Accot, J., and Zhai, S. Scale effects in steering law tasks. In Proc. of CHI'01, 2001, pp. 1-8] and Zhai [Zhai, S. Human Performance in Six Degree of Freedom Input Control. PhD thesis, University of Toronto, 1995] found that performance degraded at low and high CD gain levels. This may be partially due to limits of human motor control and limited device resolution preventing selection of every pixel at high levels, and increased clutching at low levels.
Touchpads (also called trackpads) are relative position control pointing devices that are now widely used as pointing devices in portable electronic devices such as laptop computers, mobile phones, PDA or the like. Touchpads can also be used in digitizing tablets, and for example in handheld pen tablets.
A touchpad generally comprises a touch-sensitive surface that forms the input area and is used to detect localized pressure or touch at its surface. When a user touches the touch-sensitive surface of the touchpad with a finger, or with a pointing tool (stylus or the like), the circuitry associated with the touch-sensitive surface determines and reports to the attached computer system or a computer-controlled device the coordinates of the location touched. Different known technologies for the touch-sensitive surface are used to date, and are described for example in the following U.S. patents:
A relative position control input device, like a touchpad or a mouse, will perform better than a rate control input device, such as for example a joystick [Card, C., English, W., and Burr, B. Evaluation of mouse, rate controlled isometric joystick, step keys, and text keys for text selection on a crt. Ergonomics, 21 (1978), 601-613 & Douglas, A. and Mithal, A. The effect of reducing homing time on the speed of a finger-controlled isometric pointing device. In Proc. of CHI'94, 1994, pp. 411-416]. In particular, relative position control input device, like touchpad or a mouse, enable to achieve a very precise selection (or pointing).
However, a potential issue with relative position control devices is when clutching (i.e. the momentary recalibration to avoid running out of input area) becomes more frequent, taking additional time.
The amount of clutching is dependent on the maximum area of unconstrained physical movement, referred therein as “operating range”, target distance and mapping function. A small operating range causes more clutching with large target distances, and the maximum operating range is dependent on the mapping function.
Recently, the resolution of digital displays has increased significantly, while the input area (i.e. touch-sensitive surface of the touchpad) remains fixed. This tendency renders the clutching issue more critical. For example, laptops are available with 38 cm displays (diagonal dimension) with resolutions in excess of 1400×1050 pixels, yet the touchpad input area remains at about 4 cm. With wall-sized displays, the difference is even greater.
One solution to reduce clutching in relative position control input device, like touchpads, is to increase the CD gain. But with higher CD gain, the precision performance of the input device is unfavorably decreased, especially in case of shorter movements.
The objective of the invention is to improve the existing relative position control touch-sensitive input device, in order to reduce the clutching without deteriorating the selection precision by means of user's finger or a user's pointing tool (stylus or the like).
This objective is achieved by the input device of claim 1.
The input device of the invention comprises a touch-sensitive surface forming at least one isotonic input area (ZI) and elastic abutment means forming at least one passive elastic input area (ZE) that is adjacent to the isotonic input area (ZI).
Outside the area covered by the elastic abutment means at rest, the touch-sensitive surface forms an isotonic input area for a user's finger or a user's pointing tool (stylus or the like). The elastic abutment means at rest delimit a passive elastic input area that is adjacent to the isotonic area. The terms “passive elastic area” mean an area wherein a passive elastic force is applied on the user's finger or a user's pointing tool, said passive elastic feedback force being opposed to the displacement of the user's finger or a user's pointing tool (without blocking it) and having an intensity that increases with the distance of penetration of the user's finger or a user's pointing tool in the elastic area.
Other characteristics and advantages of the invention will appear more clearly upon reading the following detailed description that is given by way of non-limiting and non-exhaustive example of the invention, and with reference to the attached drawings:
In some applications, the input device can be used as pointing device. In other applications, the device can be used for pointing and view translation. A typical example is with small screen devices like PDA where the view of a webpage, for instance, cannot fit on the entire display. In that case, the control of the pointer displayed on screen can be done using the isotonic area (ZI) of the input device, and the view can be translated using the elastic area (ZE) of the input device. When a user enters the elastic area (ZE) with his finger or with a pointing tool, the view is translated according to the direction and speed corresponding to the force vector applied.
In the particular embodiments of
The technology used for the touch-sensitive sensor 10 is not important for practicing the invention, and can be any known touch-sensitive technology, in particular any known touch-sensitive technology used in the filed of touchpad, that enables to detect a localized pressure or touch on the touch-sensitive surface 10a. Said localized pressure or touch is for example being applied on the touch-sensitive surface 10a by mean of the user's finger f (
The 2D touch-sensitive input device 1 further comprises elastic abutment means 11 that are mounted above the touch-sensitive surface 10a. In the particular embodiment of
The central area ZI of the touch-sensitive surface 10a that is delimited by the elastic abutment 110 at rest (i.e. when the elastic abutment 110 is not deformed) constitutes an isotonic input area. The annular peripheral area ZE of the touch-sensitive surface 10a, located underneath the elastic abutment 110 at rest, constitutes a passive elastic input area.
In operation, when the user's finger f or pointing tool T is positioned in the central isotonic area (ZI), it can slide freely on the touch-sensitive surface 10a without undergoing forces opposed to its displacement (with the exception of low friction forces that are negligible). When the user's finger f or pointing tool T reaches the elastic abutment 110 (i.e. the boundary between the isotonic area (ZI) and the elastic abutment 110), and penetrates in the elastic peripheral area (ZE), the elastic abutment 110 exerts on the user's finger f or pointing tool T a reverse elastic feedback force F that is opposed to the radial displacement thereof. In this particular embodiment of the invention example, this feedback force F is substantially a radial force oriented substantially toward the centre of the disk-shaped touch-sensitive surface 10a. The norm F of this feedback force increases with the radial distance (r) of penetration in the elastic area (ZE) of the user's finger f or pointing tool T. This passive elastic feedback force is a function of the mechanical properties of the elastic material in the case of a ring 110 made of elastic material, or is a function of the inflation pressure in the case of a chamber filled with a fluid (gas or liquid).
Referring to
In operation, the touch-sensitive sensor 10 reports to this control processing unit (CPU) position data [for example coordinates (x(t), y(t))] defining the instantaneous position p of the localized pressure or touch detected by the sensor 10 on its touch-sensitive surface 10a. These position data (x(t), y(t)) are defined in a 2D real space (X, Y) attached to the touch-sensitive sensor.
The control processing unit (CPU) is programmed for managing a virtual environment (EV) that is for example dynamically displayed on a screen. This virtual environment (EV) contains, for example, a virtual object (C), hereafter called cursor or pointer, associated with the user's finger f or user's tool T in the real environment.
More particularly, the control processing unit (CPU) is programmed to execute a mapping function H that computes the current output position p′(x′(t), y′(t)) of the cursor or pointer (C) in a virtual space (X′, Y′) of the virtual environment (EV), from an initial input position (x(0), y(0)) and from a relative displacement vector calculated from the previous position [(x(t−1), y(t−1)) ] and current position (x(t), y(t)) detected by the sensor 10 in the 2D real space (X, Y). The initial input position (x(0), y(0)) corresponds to the new initial input position of the finger f or tool T after clutching, i.e. when the input stream is suspended and the finger f or tool T is repositioned on the touch-sensitive surface 10a at a new position. This mapping function H uses a control display gain (CDG) to scale the relative displacement vector.
In a particular embodiment of the invention, the control processing unit (CPU) is programmed to execute two different mapping functions: one mapping function (HI) is used in the isotonic area (ZI), and one mapping function (HE) is used in the elastic area (ZE). In order to achieve a better control:
In the case of a first-order mapping function (rate control), the relationship between the input parameter (p) and the output parameter (p′) is of the integral type; in this case, The real displacement of user's finger f or user's tool T detected by sensor 10 is interpreted in terms of speed in the virtual environment (EV).
It has been tested and demonstrated experimentally by the inventors that this hybrid control (position control in the isotonic area (ZI) and rate control in the passive elastic area (ZE) has performance advantage over a pure position control when faced with significant clutching. Actually, the time that is needed to reach a target in the virtual environment with this hybrid control (position control/rate control) is faster than the time needed when only a position control is performed and no elastic abutment is being used. This hybrid control (position control in the isotonic area (ZI) and rate control in the passive elastic area (ZE) actually enables to significantly reduce the clutching, and thereby decreases the time wasted by clutching operations. This advantage is more efficient for reaching far target in the virtual environment. It has to be underlined that this improvement (clutching reduction and time saving for reaching a target) does not impair the pointing precision, because the control display gain (CDG) is not modified.
In the prior art [Dominjon, L., Lécuyer, A., Burkhardt, J. M., Andrade-Barroso, G., and Richir, S. The bubble technique: Interacting with large virtual environments using haptic devices with limited workspace. In Proc. of IEEE World Haptics, 2005, pp. 639-640], Dominjon et al disclosed a 3D hybrid position-rate control technique that use elastic feedback with a large Virtuose 6 DOF force feedback device. A spherical volume is simulated in physical space and visualized as a transparent sphere on the display. When the input point is inside the volume, movement is by position control with constant CD gain. When the input is moved beyond the spherical volume, the device uses rate control with elastic feedback.
The Dominjon et al' straightforward mapping functions (disclosed for 3D) can be adapted to 2D, and used for controlling the 2D touch-sensitive input device 1. In such a case, Dominjon et al.'s mappings (Equations (1) and (2)) introduce however trajectory and speed discontinuities when transitioning from isotonic to elastic zones. In Equation 1, the feedback force F is proportional to the distance between end effector P and the isotonic-to-elastic boundary N given spring stiffness k. The force direction is always radial with {right arrow over (r)}, the radial direction from the centre of the isotonic circle to P. In Equation 2, the input control rate V is a third degree polynomial with a scaling constant K. Dominjon et al.'s implementation set k=200 N.m−1 and K=0.03 N−3.s−1.
{right arrow over (F)}=−k·(P−N)·{right arrow over (r)} (1)
{right arrow over (V)}=K·F
3
·{right arrow over (r)} (2)
This formulation introduces a trajectory discontinuity as long as the isotonic trajectory is not radial to the isotonic circle, as illustrated on
Referring to
The pointer (on the display) will jump to the radial trajectory defined by Equation (2) the moment it enters the rate control zone, regardless of its initial path (
It is however important to achieve a continuity of speed, since a noticeable drop could affect the pre-planned trajectory, impairing user performance [Plamondon, R., and Alimi, A. M. Speed/accuracy tradeoffs in target-directed movements. Behavioral and Brain Sciences, 20, 1997, 279-349].
In order to solve this problem of trajectory and speed discontinuities, the invention further proposes novel mapping functions that enable to achieve a smooth transition from isotonic position control to elastic rate control.
The mapping functions of the invention enable to achieve a consistent trajectory by rotating and translating the isotonic-to-elastic boundary after transition; the transition velocity is also smoothed by mixing pre- and post-transition velocities. At first it appears that simply using the same isotonic direction vector (MN in
To create a consistent trajectory, the isotonic-to-elastic boundary zone is translated and rotated as the user penetrates the elastic zone. This translation and rotation of the isotonic-to-elastic boundary zone is performed smoothly, by giving mass and inertia to the boundary zone using a simple physical simulation to align it with the isotonic direction vector. The intuition behind this technique is to consider how a real circular object, like a dinner plate, would rotate and translate when pulled by a string attached to its edge (
Referring to
The novel mapping functions of the invention compute the angular speed (of the virtual pointer) at the entrance of the elastic area (ZE) (i.e. when the user's finger f or pointing tool T enters into the elastic area ZE) by using the theorem of angular momentum (Equation (3)). {right arrow over (ω)} is the rotation vector of the isotonic zone and J is its moment of inertia with a friction term (μ) added to avoid instability. The translation is proportional to the vector NP.
The inventors found that using a mass of 1 Kg and a friction coefficient of 3*10−3 N.s.rad−1 smoothes out the trajectory nicely without the sharp direction changes.
In a particular embodiment, in order to smooth the transition velocity, the novel mapping functions of the invention compute mixed velocity Vt in the elastic area (ZE) by using Equation (4), where Vo is the linear speed of the user's finger (f) or pointing tool (T) at the exit of the isotonic area (ZI), t is the time after the isotonic exit, A is a constant to adjust the mixing time (for example A=0.3 s) and K is a constant.
The invention is not limited to the particular elastic abutment 110 of the embodiment of
For example,
One skilled in the art will also acknowledge that such sensing means 12 can be also used similarly in the embodiment of
In another embodiment of the invention, the input device 1 can also comprise additional means for detecting the current position of the user's finger f or pointing tool T in the elastic input area (ZE), and for reporting this current position to the CPU. For example, the embodiment of
Number | Date | Country | Kind |
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0737020.5 | Oct 2007 | EP | regional |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2008/008397 | 10/3/2008 | WO | 00 | 4/1/2010 |