Note: Descriptions are shown in the official language in which they were submitted.
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FIELD OF THE INVENTION
The present invention relates to 6 degree-of-freedom control
devices used in human-machine interactive applications such as computer input
devices, robot controllers, machine controllers and the like.
BACKGROUND OF THE INVENTION
Various human-machine interactive areas such as telerobotics,
virtual reality and scientific data visualization are all emerging as important new
technologies, an important feature of which is the interactive human-machine
10 interface. A key component of the human-machine interface in these
applications is the control device or controller which allows users to manipulate
3 dimensional objects, real or virtual. These control devices are referred to as
6 degree-of-freedom (DOF) controllers because they have three translational
degrees of freedom and three rotational degrees of freedom. In computer
15 applications the control device is normally referred to as an input controller. The
6 DOF controller allows a user to manipulate 3 dimensional real or virtual
objects under computer control. Typical commercial computer input devices
such as the computer mouse and track ball have two degrees of freedom.
There are several different manipulation schemes available upon
20 which currently known 6-DOF input devices are based. The majority of these
manipulation schemes can be classified as either isotonic or isometric, or some
combination of these. The word isotonic literally means "equal tension" and in
relation to muscle contractions the word is defined by Webster's Ninth New
Collegiate Dictionary as: "relating to, or being muscular contraction in the
- 1
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absence of siynifica"l resistance, with marked shortening of muscle fibres, and
without great increase in muscle tone". In relation to the classification of control
devices the word isotonic refers to the general case in which the forces or
torques opposing any control input are constant. This general case therefore
5 includes the case of negligible or essentially zero opposing forces, as is the
case when a transducer is used to sense the free movement of a user's limb.
The word isometric literally means "equal measure" and in relation
to muscle contractions the word is defined by Webster's Ninth New Collegiate
Dictionary as: "of, relating to, or being muscular contraction against resistance,
10 without significant shortening of muscle fibres and with marked increase in
muscle tone". In relation to the classification of control devices the word
isometric refers to devices which sense forces and torques exerted upon them
without exhibiting significant translational or rotational displacements.
Isotonic 6 DOF input devices include the Ascension BirdTM, the
15 LogitechTM 6 D mouse, the Flying MouseTM and the PolhemusM . In all such
devices the user holds a control handle (or wears a glove) and moves his/her
hand without support. These devices usually utilize position control mapping
(pure gain control) in which the user's hand motion is sensed and proportionally
mapped to the position and orientation of a selected 3D object on a computer
20 screen. A major drawback to the isotonic position mode is its comparatively large
operating volume and resultant fatiguing which occurs from a user moving
his/her arm about unsupported. An inherent limitation of these isotonic position
control devices relates to the restricted operational range of translational motion
due to limited arm length and limited rotational movement due to limited rotation
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of the hand and arm. In the case of glove type 6 DOF input devices this
limitation is overcome by adduction wherein the user continuously clutches
(closes) and declutches (opens) their hand. When the hand is opened the
manipulated object typically remains fixed and while closed it follows the hand
5 movement. The position of the user's hand is sensed relative to a starting
position at which point the hand starts to close (adduction) and the distance
travelled is determined and mapped onto the virtual 3D object. This is not a
completely satisfactory solution since it requires potentially fatiguing
translational and rotational movement of the user's hand.
Another isotonic input control device is the immersion PROBETM
(produced by Immersion Human Interface Corporation, P.O., Box 8669, Palo
Alto, CA) comprising a stylus mounted on the end of a series of mechanical
linkages. This device works in the position control mode wherein the
manipulated 3D object moves in proportion to the movement of the stylus. While
15 the mechanical linkage system provides support to the stylus, a loose series of
linkages to give a nearly free moving stylus does not adequately support the
user's hand so that fatiguing still occurs while too tight a series of linkages
requires greater effort to move the stylus also leading to fatiguing.
The second class of 6 DOF input controllers are isometric devices.
20 Known controllers based on this principle include the SpaceballTM (US Patent
No. 4,811,608). Another device based on this principle is the Space Control
Mouse made by DFL in Germany. Isometric devices are generally used in the
rate control mode so that the force and torque applied to a control handle is
converted to a velocity of the virtual or real 3D object. A major drawback to this
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type of controller is that the user's hand operates in a substantially stationary
posture which limits the amount of somatosensory feedback experienced by the
user, as will be more fully discussed below.
Another control device, which is neither isotonic nor isometric, is
5 the CAE 6 DOF hand controller having a control grip mounted on an elastic
mounting base. A drawback to this device is that a user's control movement is
prone to being limited by the mounting base.
Investigations of target acquisition performance, for example, have
demonstrated that isotonic position control and isometric rate control have
10 certain advantages over isotonic rate control and isometric position control. One
reason isotonic position control gives better results is because it uses
movements similar to those used routinely by the user, namely free limb
movement. However, as mentioned above a drawback to the isotonic position
mode is the requirement of a large operating volume and resultant fatiguing
15 which occurs from a user moving his/her arm about unsupported.
Superior performance with isotonic position and isometric rate over
the other schemes is related to compatibility and control "feel". High
compatibility is achieved when certain properties of a particular sensing mode
(e.g. isometric) match certain modes of transfer function (e.g. rate control). For
20 example, the self-centring property of isometric devices facilitates rate control,
which may require reversed actions for stable execution of certain repositioning
and reorientation tasks.
The "feel" of a controller is related to proprioceptive feedback.
Neurophysiological research has shown that humans are equipped with at least
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four distinctive types of somatosensory receptors which form the proprioceptive
sensory feedback system and include joint receptors, Golgi tendon organs,
muscle spindles and cutaneous receptors. Each type of receptor is responsible
for detecting specific stimuli and inputting the information to the central nervous
5 system with the latter integrating the various types of input.
A drawback to the known 6 DOF input devices discussed above
is that none make full, simultaneous use of all available somatosensory
receptors. For example, during use of an isometric controller such as the
Sp~ceb~ll the joint angles in a user's arm are usually stationary so that generally
10 only the force sensitive Golgi tendon organs and cutaneous receptors on the
finger tips are utilized.
Accordingly, it would be advantageous to provide a 6-DOF control
device which more fully utilizes the human somatic information feedback system
and which does not result in rapid fatiguing.
SUMMARY OF THE INVENTION
The present invention provides a six degree-of-freedom control
device which more fully utilizes the somatosensory feedback system receptors.
In one aspect the present invention provides a six degree-of-
20 freedom control device for controlling movement of a real or virtual object. Thedevice comprises a member adapted to be moved by a user, a support means
operably coupled to the member for supporting the member in a rest position,
the member being translationally and rotationally movable from the rest position
in suL.slanlially any direction. The support means includes restoring force means
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for developing a restoring force when said member is moved from said rest
position to urge the member back to the rest position. The device is provided
with a sensor means for sensing the position and orientation of said member
with respect to said rest position. A processor means is connected to the sensor
5 means for processing the sensed position and orientation of said member to
provide information for controlling the motion of a real or virtual object being
manipulated by the control device. The control device can be operated in a
mode selected from the group consisli,lg of velocity control mode, a combination
of position and velocity control mode, and higher order control modes.
In another aspect of the invention there is provided a hand
operated six degree-of-freedom control device for controlling movement of a real
or virtual object. The device comprises a hand grip member and a support
means operably coupled to the hand grip member for supporting the hand grip
member in a rest position. The hand grip member is translationally and
15 rotationally movable from the rest position in substantially any direction. The
support means includes restoring force means for developing a restoring force
when said member is moved from the rest position to urge the member back to
the rest position. The control device is provided with a sensor means for sensing
the position and orientation of the hand grip member and a processor means
20 connected to the sensor means for processing the sensed position and
orientation of the hand grip member to provide information for controlling the
motion of a real or virtual object being manipulated by the control device. The
control device may be operated in a mode selected from the group consisting
of velocity control mode, a combination of position and velocity control mode,
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and higher order control modes.
In another aspect of the invention there is provided a method of
supporting a hand grip member in a six degree-of-freedom controller. The
method comprises supporting the hand grip member in a rest position under
compliant tension so that it can be translationally and rotationally moved in any
direction away from the rest position whereupon the hand grip member is urged
back to the rest position.
BRIEF DESCRIPTION OF THE DRAWINGS
The 6 DOF control device forming the present invention will now
be described, by way of exa",p'e only, rererence being had to the accompanying
drawings, in which:
Figure 1 is a perspective view of a 6 DOF control device
constructed in accordance with the present invention;
Figure 2(a) is a perspective view of the control device of Figure 1
being moved translationally by a user;
Figure 2(b) is a perspective view similar to Figure 2(a) but with the
controller undergoing rotational movement;
Figure 3 is a view along arrow 3 of Figure 1;
Figure 4 is a view along arrow 4 of Figure 1;
Figure 5 is a perspective view of another embodiment of a 6 DOF
controller constructed in accordance with the present invention;
Figure 6 is partial sectional view, broken away, of a tensioning
device forming part of the present control device;
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.
Figure 7 is a perspective view of a 6 DOF controller of the present
invention including an acoustic position sensor mounted thereon;
Figure 8 is a perspective view of a 6 DOF controller including a
mechanical position sensor coupled thereto;
Figure 9 is a diagra,ll",alic representation of a human-machine
interactive system using the present 6 DOF controller as the input controller;
and
Figure 10 is a partial sectional view of an alternate embodiment of
a connector member showing the connector of Figure 6 modified to include a
damping member in parallel with part of the connector.
DETAILED DESCRIPTION OF THE INVENTION
Referring first to Figures 1 and 2 there is shown generally at 20 a
six degree-of-freedom (DOF) control device embodying the present invention.
Cont,oller 20 includes a manipulator 22 which is shaped and dimensioned to be
readily gripped by either the fingers or palm and fingers of a user's hand.
Manipulator 22 is adapted to be operated by a user's appendage preferably the
hand so that manipulator 22 is a hand grip member. Manipulator 22 as shown
is ellipsoidal in shape but it will be appreciated by those skilled in the art that
it may be of any shape as long as it is adapted to be col~rol lably gripped by auser. Manipulator 22 is provided with a rubbery outer coating designed to
improve the user's grip in order to prevent slipping of the fingers during
movement of the manipulator. This tacky outer surface permits manipulator 22
to be moved with less force than would be required for a manipulator with a
21 84038
smooth slippery outer surface and in addition it enhances cutaneous haptic
fee~h~ck.
Manipulator 22 is supported within a support means comprising a
frame 24 and connectors 26. Manipulator 22 is supported under compliant
5 tension which means the manipulator can be moved both rotationally and
l,anslalionally with respect to the rest position. Connectors 26 are each attached
at one end thereof to manipulator 22 and at the other end to frame 24. Frame
24 is shaped and dimensioned to provide ready access to a users hand for
gripping manipulator 22 and to allow for both translational and rotational
10 movement of the manipulator within the frame as shown in Figures ~(a) and (b).
Connectors 26 must satisfy two functional requirements the first being to
facilitate rotational and translational movement of manipulator 22 and the
second being to return the manipulator to the null or rest position upon releaseof tension thereby providing a self-centring function. Release of tension refers15 to a user allowing manipulator to return to the rest position under user control
not necessarily physically releasing the manipulator. Connectors 26 are
therefore preferably elastic in nature so that they may be stretched and twistedthereby satisfying these two requirements. The preferred manipulator support
is refe"ed to herein as an elastic support which means that manipulator 22 may
20 be moved translationally or rotationally in any direction and doing so builds up
a reslori"g force which acts to promptly urge manipulator 22 to the null position
when it is released. In the null or rest position manipulator 22 is in a
predetermined spatial position and orientation. Figure 1 illustrates controller 20
in the null position and connectors 26 provide sufficient tension to hold
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manipulator 22 firmly in this position. Figures 3 and 4 illustrate top and front view
of connectors 26 connecting frame 24 and manipulator 22.
It will be appreciated that frame 24 may take on a plurality of
shapes with the prime design considerations being that a user be able to
5 comfortably grip manipulator 22 without undue stress on his/her arm and wrist
and that connectors 26 are spaced apart sufficiently so as not to interfere with
the fingers.
In one embodiment the manipulator may be spherical with the
connectors symmetrically disposed about the manipulator to provide a
10 subslar,lially uniform compliance in all directions for both rotational and
l,dnslalional movements and re~ ri,)g forces urging the manipulator back to the
null position. However, it is not essential that the compliance and developed
restoring forces be symmetric. The structure of controller 20 has several axes
of symmetry and manipulator 22 may be more easily rotated about the vertical
15 major axis of the ellipsoid than about the minor axis. The elastic connectors 26
need not necessarily be disposed symmetrically about manipulator 22.
The present controller with the elastic support operates between
the extrema of isometric and isotonic sensing modes. The relative contribution
of isometric to isotonic operation of the device may be governed by the tension
20 on connectors 26. As the tension on connectors 26 is increased, the operation
of the controller shifts further towards the isometric sensing mode since it
becomes more difficult to move manipulator 22. Therefore, by adjusting the
tension on connectors 26, the controller may be customized to the particular task
at hand.
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Figure 5 illustrates a controller 30 wherein each connector 26 is
attached to a tensioning device 32 which in turn is attached to frame 24.
Tensioning device 32 includes a bobbin 34 which when rotated increases or
decreases tension on connector 26, depending on direction of rotation.
5 Adjusting tensioning device 32 serves to fit the specific task and individual
preference.
Connectors 26 may be fabricated of various materials including
elaslorileric materials or springs. Figure 6 illustrates a connector 40 comprising
a cable portion 42 having a spring 44 attached at one end thereof. Attached to
spring 44 is a tensioning device 46 including a threaded shaft 48 and two nuts
50 threaded onto shaft 48, with a nut located on each side of frame 24. The null
position of manipulator 22 relative to frame 24 is set by adjusting the tension on
cable 42 by increasing or decreasing the length of spring 44 using nuts 50.
Connectors 26 may include a damping or viscous resistance element in parallel
with the elastic connector portion. Referring to Figure 10 there is shown at 110
a connector similar to that shown in Figure 6 including a diagrammatic
representation of a viscous resistance element 112 connected in parallel with
spring 44.
While the controller as described herein is specifically adapted to
20 be manipulated by a user's hand, those skilled in the art will appreciate that the
controller may be adapted to be used by other appendages of the user such as
his or her foot.
The controller of the present invention distinguishes over previous
controllers in that the manipulator is suspended and elastically supported to
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permit both rotational and translational movement while many currently available
controllers are either free moving or mounted on a base. The base mounted
controllers are restricted from being moved translationally away from the base
and cannot ul ,deryo rotational movement in all directions about the centre of the
5 manipulator.
As discussed above, the sensing mode of the elastic input
controller of the present invention resides part way between the extremum of
isotonic operation and the extremum of isometric operation with the result that
the self-centring elastically mounted manipulator 22 more fully utilizes the user's
10 somatosensory feedback system. In other words movement by a user's hand
excites all known types of proprioceptors in the limb including the Golgi tendon
organs, the cutaneous receptors, the joint receptors and the muscle spindles
thereby producing a superior control "feel" and hence user performance. This
results in a significant advantage of the present controller over previous
15 controllers. Another advantage relates to the fact that manipulator 22 may be
operated solely by a user's fingers which have a higher dexterity than a user's
palm thereby more fully utilizing the somatosensory information from the fingers.
Further, since the range of translational movement is confined to the interior of
frame 24, the user's arm may be partially supported on the elbow which in turn
20 can be supported by a height adjustable elbow rest thereby considerably
reducing fatiguing. The frame is preferably rigidly fixed and the user may adjust
the arm or elbow rest to find the most comfortable position.
In addition, the self~enl, i"g function of the compliant manipulator
support to return manipulator 22 to the null position facilitates operation of the
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device in the rate control mode. In rate control mode, repositioning and/or
orienl~tion of the real or virtual 3D object requires reversed actions. In order to
make an object stop at a certain position the input must return to zero. In the
rate control mode the information input to the computer is converted to a velocity
5 of the 3D object. A major advantage of rate control mode therefore is that the
object may be moved in an unlimited range, both translationally and rotationally,
without the restriction of the hand limit.
Various sensor schemes are commercially available for sensing
the position and orientation of manipulator 22. In general, a field sensor may be
10 mounted on the back exterior surface of manipulator 22 or alternatively the
sensor may be located in the interior of manipulator 22 and a transmitter placed
in prc"~i",ily to the marip~ tcr. The transmitter emits a signal which is detected
by the sensor and the position and orientation of the sensor and hence
manipulator 22 are determined and inputed to the control program to be
15 transformed into movement of the 3D object.
One field sensing device which may be used in the 6 DOF control
device of the present invention is based on a magnetic detection system. This
system comprises a receiver with several anlennas which detect signals emitted
by a transmitter and inputs the calculated position and orientation to the host
20 computer. The above mentioned Polhemus sensor utilizes an AC magnetic field
while the Ascension Bird utilizes a pulsed DC magnetic field. Those skilled in
the art will readily u"dersland how such sensor systems may be adapted for the
present device. When the 6 DOF controller of the present invention uses
magnetic detection the receiver is preferably mounted on the interior of
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manipulator 22 and the transmitter located in proximity to the controller support
frame 24. A further advantage of the control device of the present invention is
that because manipulator 22 is confined to movement within frame 24, there is
no need for expensive long range transmitter technology as is required with for
example glove devices. The transmitter may be mounted on the frame or in
close proximity thereto and as a consequence more economical transmitter
equipment may be used.
Another position and orientation sensing device which may be
used with controller 20 is an acoustic system such as the LogitechTM 6D sensor
sold by Logitech Inc. Fremont CA. Referring to Figure 7, ultrasonic pulses are
emitted by a generally triangular array of ultrasonic sources 70 and the pulses
are detected by 3 miniature microphones 72 mounted on exterior surface of the
rear side of manipulator 22 away from the user's hand. It will be appreciated bythose skilled in the art that while ultrasonic systems are prone to line-of-sight
occlusion they may still be advantageously employed with the 6 DOF input
control device of the present invention by careful positioning of sources 70 andmicrophones 72 as shown in Figure 7.
Figure 8 illustrates a mechanical sensing means shown generally
at 80 cor,lprising a plurality of rigid mechanical linkages 82 connected betweenmanip~ or 22 and a base 84. The ends of acljacenl linkages 82 are connected
to joints 86 which include potentiometers which give an output signal related tothe location and orientation of the linkages. The various signals are processed
to give the translational and rotational position of manipulator 22.
The information generated by the present 6 DOF control device is
14
2 1 84038
processed using any one of several known methods to map the 6 DOF
in~o",)alion to the motion of the physical or virtual object 3D being manipulated
by the control device. Figure 9 illustrates a typical configuration including
controller 90 in which manipulator 22 is wired to an electronic unit 92 which
5 calculates the position and orientation of manipulator 22 with respect to the
transmitter. The output of unit 92 is inputed into computer 96 which translates
the position of manipulator 22 into a position and/or velocity for the real or virtual
3D object being controlled by controller 90. Typically the controller of the present
invention is used in rate or velocity control mode but in special circumstances
10 may be used in a combination of position and rate modes, or even higher
derivatives including for example acceleration and angular velocity to mention
a few. The control software used in such systems typically employs techniques
such as non-linear gain, filtering and thresholding as will be known to those
skilled in the art. The computer software can be used to adjust the control gains
15 and other parameters on each degree-of-freedom according to the physical
structure of the manipulator device so that the user has a "harmonized" control
feel.
The results of studies comparing the present 6-DOF controller
which more fully utilizes the somatosensory feedback system with known
20 isometric rate controllers reveal that subjects learn faster in using the elastically
supported manipulator and fatiguing is considerably reduced.
While the 6 DOF control device forming the present invention has
been described and illustrated with respect to the various embodiments
disclosed herein, it will be appreciated by those skilled in the art that numerous
21 84038
variations of these er"bodi",ents may be made without departing from the scope
of the invention.
16
