Device for use in manual control of the movement of a real or imaginary object

An apparatus for providing translational and rotational control signals comprises a base; a handle; and a suspension system operable to resiliently couple the handle to the base such that the handle may be freely moved in translational and rotational directions relative to the base and to move the handle to a neutral position when no forces are applied to the handle. The suspension system includes a plurality of suspension members each having an orientation axis, the suspension members being disposed such that respective pairs of the orientation axes are orthogonal to each other; and a plurality of sensors, each sensor having a pair of sensor components, at least two sensors being coupled to each of the suspension members and operable to sense translational and rotational movement of the respective suspension member along its orientation axis, the sensors producing output signals indicative of the translational and rotational movement of the handle with respect to the base.

FIELD OF THE INVENTION 
The invention relates to an apparatus for manual control of a real or 
imaginary object and is of the type in which an operator applies forces 
and torques to a handle. 
BACKGROUND OF THE INVENTION 
Apparatuses of the above type may be used in the same way as a commonly 
known "joystick". The operator grasps the handle of the apparatus and 
thereby applies forces which, both in respect of direction and size, 
reproduce the move-ment which the operator wants a controlled object to 
perform. As a function hereof the apparatus emits signals which contain 
unambiguous information--both in respect of direction and size about the 
strain applied by the operator to the handle and which can therefore be 
utilized by the controlled object or by an intermediate control system for 
operating accordingly. 
A joystick often has a substantial degree of movability and is generally 
used with a high translational or angular movement of the handle of the 
joystick that it can distinctly be felt by the operator. The emitted 
signal is proportional to the movement of the handle, and the joystick is 
most often biased by a relatively weak return spring towards its neutral 
position. Apparatuses of the type mentioned by way of introduction may, 
contrary to this, be designed in such a way that the handle is rigid or 
nearly rigid relative to the rest of the apparatus. A strain applied by 
the hand of the operator will not entail any noticeable or visible 
movement of the handle relative to the rest of the apparatus. Admittedly, 
even so rigid a construction will always move more or less when a force or 
a torque is applied, but the movement may be so small that it is not 
noticeable to the operator. 
In EP-B 227,432, U.S. Pat. No. 5,222,400 and WO 93/4348 an apparatus is 
disclosed, in which six arms in the form of leaf springs and radially 
positioned in three mutually orthogonal pairs are slidably seated in the 
handle, the arms of each pair extending along one and the same axis and 
the arms in combination connecting the handle with the support. 
For detecting the movements of the handle the apparatus is provided with 
three pairs of sensing means for sensing the translation and the rotation 
of the handle relative to the support. The sensing means is, with respect 
to each arm, provided with a light source and a light sensor which are 
fastened to the frame by means of suspensions, as well as a movable 
shutter fastened to the remote end of the arm. Each pair of sensing means 
can thus sense displacement of the handle relative to the frame in the 
direction of one axis perpendicular to the axis which connects the two 
means of the pair, and rotation of the handle relative to the support 
about a third axis perpendicular to both these axes. 
Said slidable seating is a condition for the translatory movability of the 
handle when the arms are arranged in the above-mentioned way; the arms are 
in practice not deformable in their longitudinal direction, and each pair 
of arms would otherwise oppose translatory movement of the handle along 
this axis. 
The slidable seating is also a prerequisite for using arms in form of leaf 
springs, as they are practically not deformable in the direction 
transverse to the longitudinal axis of the arm and transversely to the 
desired direction of deformation; each pair of arms which extends along 
the same axis would otherwise oppose both rotation of the handle about one 
of the axis perpendicular to said axis and translatory movement of the 
handle along the second one of the axes perpendicular to said axis. 
Such a slidable seating has been obtained by providing the end of each leaf 
spring (arm) with a ball engaging a slot in the handle in the form of a 
slit-shaped interspace between two plane-parallel walls, said interspace 
having the same diameter as that of the ball and extending in the plane of 
the leaf spring in question. 
The slidable seating of the arms is theoretically ideal in respect of 
providing a correct resolution of the forces and torques applied by the 
operator to the handle into unambiguously corresponding deflections of the 
six leaf springs, but entails, however, several considerable, practical 
drawbacks. 
One considerable drawback of the construction is that it is mechanically 
complicated, as it consists of many mechanical components which are to be 
assembled when the apparatus is manufactured, which makes the manufacture 
difficult. In this connection, the apparatus cannot be divided into 
subassemblies or groups of components which in a simple way can be 
exchanged when repairing. The apparatus is, to judge from the 
publications, to be assembled from the inside and towards the outside, all 
its individual parts having to be mounted in a fixed order. 
Another considerable drawback is that the sliding bearing, where the leaf 
springs engage the shell of the ball--unless it has been manufactured with 
a precision which is virtually unattainable--would cause an undesired 
mechanical play. The play may also occur under use by wear and tear of the 
bearing parts, a possible high precision in the bearing thus being ruined. 
This precision may also be ruined by the fact that apparently some of the 
interspaces are positioned in zones, where the ball-shaped handle is 
divided in two parts. 
The play may i.e. cause the ball to "rattle" where it is engaging the ball 
shell, such that the whole construction, when exposed to vibrations, has 
unpredictable mechanical resonance frequencies and strong resonance 
oscillations. The apparatus then becomes unfit for use in a 
vibration-filled environment. The play may also have the effect that it 
becomes unclear to the user where the neutral position ends and the 
starting of a movement begins. Furthermore, the presence of play will have 
the effect that the obtained movement of the periphery of the ball as a 
consequence of the application of a given torque or a given force becomes 
bigger than it was before the play arose. 
Finally, it is a substantial drawback in this prior art apparatus that, to 
judge from the publications, it will be very vulnerable for an 
unintentional overloading. Even though there seems to be rigid arms 
limiting the deflection of the afore-mentioned arms, this limitation takes 
place some distance from the ends of these movable arms, and the remote 
part of the arms with the ball is thus completely unprotected against 
overloading. 
From WO-PA 95/3527 an apparatus of the same type is known, in which three 
arms which are placed radially in the same plane and connect the handle 
with the support are slidably seated in the handle. 
This slidable seating is likewise a condition for translatory mobility in 
certain directions of the handle with this arrangement of the arms: the 
arms are in practice not deformable in their longitudinal direction, and 
each arm would otherwise oppose translatory movement of the handle along 
its longitudinal direction. 
The slidable seating is presumably a prerequisite for unambiguously 
detecting the deflection of the arms. This cannot, however, be said with 
certainty, as the publication is very unclear in this respect. 
The slidable seating has here been obtained by shaping the end of each arm 
(which has the shape of a thin rod) as a part of a spherical surface 
engaging a circular cylindrical bore with radial axis in the handle. 
This slidable seating entails also in this case several considerable, 
practical drawbacks of the same kind as described above. 
Even though this construction is less complicated than the one described 
above, it also comprises many mechanical elements which have to be 
assembled during the manufacture of the apparatus, which to judge from the 
publication has to take place from the inside towards the outside, all its 
individual parts having to be mounted in a certain order of succession. 
SUMMARY OF THE INVENTION 
The invention provides an apparatus of the type mentioned by way of 
introduction, in which apparatus the above-mentioned drawbacks have been 
eliminated, and simultaneously a good precision, reproducibility and 
resistance towards vibrations have been obtained, and which apparatus is 
particularly simple and cheap to manufacture. 
This is obtained according to the invention by means of connecting 
suspension elements to both a support and a handle without the use of 
joints or bearings to obtain a jointless and solely elastically deformable 
suspension of the handle relative to the support. The resiliency is 
attained by the suspension elements themselves and/or their connections to 
the support and/or the handle, respectively, being resilient. As there are 
no joints or bearings demanding a high precision and being subject to wear 
and tear during use or by vibrational stress, the above-mentioned 
drawbacks have been eliminated, the suspension elements at the same time 
becoming simpler and cheaper to manufacture. 
By forming the suspension elements integrally with a handle, a particularly 
simple and cheap embodiment of the jointless connections is obtained and a 
safe control of the two fastening means relative to each other during the 
handling of the suspension elements prior to their being mounted in the 
apparatus is achieved. 
Making the suspension elements elongate and extending in an L-shaped curve 
ensures in a simple and cheap way the deformability of the suspension 
elements in all directions such that they do not oppose movement of the 
handle with respect to the support in the longitudinal directions of the 
elements. 
According to another feature of the invention, the suspension elements are 
placed as remote as possible from each other within the possibilities 
given by the outer dimensions of the apparatus. Thus, a lesser sensitivity 
to torque compared to the sensitivity to translatory forces is obtained. 
Tests have shown that practically all test persons underestimate the 
torque they apply to such an apparatus compared to applied translatory 
strain, and such a reduced sensitivity is therefore desirable. 
Moreover, this measure makes the elastic deformations correspondingly 
bigger by rotation of the handle, whereby an improved repetitive accuracy 
is attained and a better defined neutral position of the handle. 
By including slits having variable widths, a considerable reduction of the 
undesirable light diffusing from the light source in one sensor means to 
the light sensor in a second sensor means is obtained. Thus, time 
multiplexing of the light of the various sensor means in the apparatus may 
be avoided. 
By making the shutters integral with the fastening means, a particularly 
cheap embodiment of the shutters is obtained and at the same time a good 
reproducibility in their position relative to the fastening parts. 
Another feature of the invention is to include a stop for the movement of 
the shutters when they are moved away from each other, which stop is 
simple and inexpensive. Tests and calculations have shown that these stops 
are strong enough to withstand even a sturdy person about to fall grasping 
the handle of the apparatus. 
By fastening a light source and detector to one of the shutters, a simple 
and cheap mounting of light source and light sensor with good 
reproducibility is obtained. 
By fastening a pair of sensor members to one of the shutters, a suspension 
member is obtained which constitutes one component which is easy and safe 
to handle; simple to mount and which can be quickly replaced for repair, 
the apparatus according to the invention becoming particularly simple to 
assemble during the manufacture and to disassemble for repair. 
By making the distance between two sensor members which have been fastened 
to one shutter greater than about 80% of the extension of the sensor 
element, a more safe sensing of the rotation of the handle is obtained. 
The invention also includes the feature that forces and torques along 
several mutually perpendicular axes can be sensed.

DETAILED DESCRIPTION OF THE INVENTION 
Identical reference numbers are used for corresponding parts in all 
figures. 
FIG. 1 shows a preferred embodiment of an apparatus according to the 
invention. A ball-shaped handle 1 is suspended on a support 5, the lower 
part of which is visible in FIG. 1. The support 5 is fastened to a base 
not shown which is stationary and stable relative to the operator. 
The apparatus according to the invention may for instance be used for 
control of a machine which can move in three dimensions, such as an 
excavator or the like, an operator pressing or twisting by a simple 
application of strain by the hand the handle of the apparatus in the 
direction and with the strength desired for the movement. 
For control of such machines it is a substantial advantage of the apparatus 
that it is without bearings and joints, as these would substantially 
increase the risk of damage to the apparatus when used in cases where 
strong vibrations may occur. 
The apparatus may also be used in a similar way in situations where a 
person is to control apparatuses, such as robot arms or manipulator arms, 
machine tools for processing in three dimensions, such as milling in 
connection with "fast prototyping", or movable objects, including 
imaginary objects which are shown on a computer display or the like. The 
apparatus will also be suitable in programming robots which are to 
simulate the movements of an operator. 
The apparatus can also be used for control of vehicles, such as 
helicopters, manned or remote-controlled submarines and other crafts 
movable in three dimensions. 
The applicability of the apparatus within other fields will be understood 
by a person skilled in the art. 
The suspension of the handle 1 is disposed in such a way that the handle 1 
can be moved slightly in all directions, both by translation and by 
rotation. The possible movements are, however, preferably so small that 
the operator does not perceive them when the apparatus is operated 
manually. The suspension is as far as possible ideally elastic, i.e. there 
is a proportional and unambiguous relationship between the strain applied 
to the handle by the operator and the resulting movement of the handle. 
For sensing the strain applied to the handle by the operator it is thus 
sufficient to sense the resulting movements of the handle which may be 
resolved in displacement (translation) and turning (rotation). 
For detecting these movements--which as previously mentioned preferably are 
very small--a suspension member 22 like the one shown schematically in 
FIG. 2 is used in the embodiment shown. The suspension member 22 comprises 
two displacement sensor means and two suspension elements. These are in 
the figure shown schematically as the two hatched areas 10. 
The suspension member 22 is substantially planar, extending in the plane of 
the drawing and is provided with two fastening parts, viz. an outer 
fastening part 12 and an inner fastening part 9, by means of which the 
suspension member can be fastened to the support and/or the handle, 
respectively, (or the reverse). In the embodiment shown the fastening 
parts 9, 12 are provided with bolt holes 23, 24 for fastening. 
By means of the suspension member 22 shown in FIG. 2, forces can be 
detected in the direction 11, which is in the plane of the drawing, and 
torques in the direction of rotation 14, i.e. about axes perpendicular to 
the plane of the drawing. The strains are to be applied to the suspension 
member between the two fastening parts 9, 12, for instance such that the 
fastening part 12 is kept stationary and the strain, which is to be 
sensed, is applied to the second fastening part 9. 
The resilient suspension elements, which are part of the two hatched areas 
10, will deform if the suspension member is subjected to said strains, 
such that both suspension elements will deform by pull or pressure in 
opposite directions, if a torque in the rotational direction 14 is applied 
to the suspension member. 
The deformations are sensed by the displacement sensor means arranged 
together with the suspension elements which emits a signal which is 
preferably electrical, when subjected to such a strain. The displacement 
sensor means in the areas 10 are preferably constructed in such a way that 
by deformation in the direction 11 they emit a significantly stronger 
signal than by deformation in other directions. 
A person skilled in the art will realize that the pairs of suspension 
elements and displacement sensor means in practice constitute force 
transducers, and the function of the apparatus is easier to understand, if 
the hatched areas 10 are regarded as ideal force transducers. 
Reference is now made to FIG. 3, which schematically shows the interior 
structure of an embodiment of the apparatus according to the invention. 
The main apparatus comprises a support 5, a construction 6 with three 
suspension members 22 and a handle 7 which the operator grasps. These 
three major parts 5, 6, and 7 are for the sake of clearness shown 
disassembled from each other in FIG. 2. 
The three suspension members 22 are also designated by the letters A, B. 
and C, and are placed in mutually perpendicular planes. Three mutually 
perpendicular axes 15, 17, 19 are normal to these planes. 
When looking at FIG. 3 it will be realized that the suspension member 22A 
can sense forces in the direction 19 and torques 20 about the axis 15; the 
suspension member 22B can sense forces in the direction 15 and torques 16 
about the axis 7; and the suspension member 22C can sense forces in the 
direction 17 and torques 18 about the axis 19. 
As a force in any direction may be resolved in force components in the 
three directions 15, 17, 19, and a torque about any axis may be dissolved 
in torque components in the three rotational directions 16, 18, 20 (i.e. 
in torque components about the three axes 17, 19, 15), any compound 
application of force and torque may be detected by the suspension members 
22 and dissolved in components in three said mutually perpendicular 
directions. 
By means of suitable data processing, for instance in a computer, the 
resolution into components may be transformed from or to any desired 
coordinate system, Cartesian, non-orthogonal or polar. There is thus no 
practical limitation of the orientation of the three suspension members 
shown in FIG. 3. 
When assembling the apparatus according to the invention, the handle 7 is 
displaced downwards in FIG. 3, such that the triangular pyramid apex 8 
abuts all three interior fastening parts 9, and the support 5 is displaced 
upwards in the figure, the frustum 21 of a triangular pyramid abutting all 
three outer fastening parts 12. The interior fastening parts 9 are 
fastened to the handle 7 and the outer fastening parts 12 are fastened to 
the support 5. The fastening may take place in any suitable way, for 
instance by means of screws, which are screwed into the pyramid 8 and the 
frustum 21 of the pyramid through the bolt holes 23 or 24, respectively. 
Gluing, soldering, moulding in place or welding may also be used. 
The handle 7 is practically usable as the embodiment shown in FIG. 3, but a 
different and better design might easily be possible. In a practical 
embodiment the handle 7 may have the shape of a ball shell encompassing so 
much of the construction 6, that only the connection to the support 5 is 
not encompassed, and internally being provided with a triangular pyramid 
with the same shape as the pyramid 8 shown in FIG. 3. Thus, the apparatus 
assumes the preferred embodiment shown in FIG. 1. 
It is seen from FIG. 3 that assembly and disassembly of the apparatus 
according to the invention may be performed in a very simply way. The 
suspension members 22 may thus be screwed one by one onto the support 5, 
whereafter the handle is screwed onto the suspension members. When the 
handle 1 is ball-shaped, as shown in FIG. 1, it is preferably shaped as an 
upper part of a ball, which on its bottom side has the triangular pyramid 
8, in addition to a bottom part of a ball shell with an opening for the 
support 5, the lower part being placeable on the support from below and 
fastenable to the upper part in any way after the assembly of the 
apparatus. 
A preferred embodiment of a suspension member 22 according to the invention 
is shown in FIG. 4. The mechanical part of the suspension member 22 is in 
this embodiment cut from a single plate 34, preferably a plate of spring 
steel, the dimensions of which can be seen from FIG. 4. 
The cutting is most preferably made by laser beam or water-jet cutting. 
In this embodiment the suspension elements are elongate and substantially 
L-shaped, each comprising two straight portions 25 and 26. The portions 25 
are made integrally with the interior fastening part 9 and the portions 26 
integrally with the outer fastening part 12. Each portion 25 has the 
effect of a resilient, bendable bar. 
It is important that the suspension elements be flexible in all directions, 
as they would otherwise opposed movement of the handle 1 in certain 
directions. This flexibility in all directions is exactly ensured by the 
L-shape 25, 26 shown in FIG. 4. 
The plate 34 of the suspension member is designed with a right-angled 
cut-out 42 which makes it possible to place the three suspension members 
22 orthogonally in the mutual engagement shown in FIG. 3, the cuttings 42 
engaging each other. 
Portions 35, 36 of the interior fastening part 9 and the outer fastening 
part 12, respectively, are positioned oppositely and form two slits 30 in 
between them. These portions 35, 36 constitute shutters. Together with 
photo-electric means 37 the shutters 35, 36 constitute two sensor means 
38. 
The suspension member 22 can sense forces along an axis 40 positioned in 
the plane of the plate 34 and perpendicular to an axis 39 connecting the 
two sensor means 38. The axis 40 corresponds to the direction 11 in FIG. 
2. Moreover, the suspension member 22 can sense torques about axes 41 
which are perpendicular to the axes 39 and 40. Torques about the axes 41 
correspond to torques in the rotational direction 14 in FIG. 2. 
The structure of the sensor means 38 is shown more detailed in FIGS. 5 and 
6. 
FIG. 5 is a sectional view along the line V--V in FIG. 4. An optical 
transducer, more precisely a light emitter 32, such as a light-emitting 
diode LED, is in a manner not shown in detail mounted on the bottom side 
of the suspension member 22 fastened to one of the two shutters 35, 36 
opposite the slit 30 between the shutters. A second optical transducer, 
more precisely a light-sensitive electronic component 31, such as a 
photodiode, is in the same way mounted on the top side of the suspension 
member 22, opposite the light-emitting diode LED 32. The diode emits a 
beam of light 33, which impinges on the photodiode 31 through the slit 30. 
It is important that the distance between the sensor means is as big as 
possible to attain large signals and subsequently a high signal-to-noise 
ratio by rotation of the handle 1. This is made possible by use of as 
small components (light-emitting diodes 32 and photodiodes 31) as 
possible. Particularly suitable are SMD components (Surface Mounted 
Devices), as they are small in themselves. Suitable types are for instance 
the light-emitting diode from Siemens, LS S260-DO and the photodiode 
Siemens BP 104 S. 
When the outer fastening part 12 and the interior fastening part 9 are 
pressed together (in direction towards each other) with a force in the 
direction 11, the portions 25 will deflect outwards, exerting a reaction 
spring force. By the deflection of 25 the slits 30 between the shutter 36 
on the outer fastening part 12 and the shutter 36 on the interior 
fastening part 9 become narrower. When the force applied is suspended, the 
deflection of 25 will cease and the slit 30 will regain its original 
width. Contrary to this the slit 30 will become wider, if the applied 
force mentioned above goes in the opposite direction (pulls the fastening 
parts 9, 12 apart). 
The photodiode 31 acts in this connection as a light meter measuring the 
light passing through the slit 30. When the width of the slit is reduced 
on account of an applied force, as described above, the width of the light 
bundle 33 is reduced, whereby the amount of light falling on the 
photodiode 31--and consequently its output signal--is correspondingly 
reduced. Contrary to this the output signal from the photodiode 31 is 
increased when the width of the slit 30 is increased. 
FIG. 6 shows the slit 30 between the shutter 36 on the outer fastening part 
12 and the shutter 35 on the interior fastening part 9. The slit will in 
itself limit the movement of the two fastening parts, when they are moved 
towards each other, the slit simply closes when the shutters contact with 
each other. Limitation of the movement away from each other of the two 
fastening parts is in a similar way made by two means 27, 28 formed in the 
plate 34 and engaging each other behind, a second slit formed between 
them. This limitation of the mutual movement of the two fastening means 
has by tests and calculations proved most effective, as it in itself can 
resist a force applied by a sturdy person about to fall and then grasping 
the handle of the apparatus. 
When a force perpendicular to the axis 40 is applied to the fastening 
parts, i.e. not in the desired working direction of the suspension member 
22, the portion 25 and/or the portion 26 of the suspension element will 
deflect in a direction which is dependent on the direction of the force. 
Thus, the shutters 35 and 36, which are opposite each other on each their 
side of the slit 30, will be displaced relative to each other, but in such 
directions that the effective distance between the shutters--and 
consequently the light transmittance--is only insignificantly changed. 
Even though the suspension elements in the above embodiment are shown in 
the same number (six) as the sensor means and positioned immediately next 
to them, there is nothing preventing the suspension elements from being 
differently constructed or from being present in a different number. The 
flexible suspension system may for example be constituted by a flexible 
column extending along the vertical symmetry axis of the apparatus. The 
suspension members may then have a similar construction as described above 
provided that cut-outs be made in the interior fastening parts 9 around 
the symmetry axis of the apparatus.