Platform mountings

A platform is mounted by bellows, at least one for each degree of freedom (DOF) of the platform. The bellows may provide either an active or a passive mounting for the platform. By arranging a suitable number of such bellows in supporting relationship a platform or floater for example six degrees freedom can be provided. Using pneumatic bellows in opposed pairs, one pair for each degree of freedom and by controlling the pressure in (and flow to) the bellows selected forces may be applied to the platform to accurately position the platform or to provide feedback for a sensory control e.g. as reflected force applied to the joystick. The position and orientation of the platform, i.e. movement of the platform, may be used to generate signals for example as in a joystick. Sensing the pressure in each of the bellows of each of the pairs permits the forces being applied by or to the platform to be monitored.

FIELD OF THE INVENTION 
The present invention relates to pneumatic mounting of a platform. More 
particularly the present invention incorporates bellows to mount the 
platform to facilitate monitoring or controlling the desired interaction 
between the platform and its stator. 
BACKGROUND OF THE PRESENT INVENTION 
The requirements for fast acting interconnecting joints in manufacturing, 
robotics, teleoperation equipment, etc., with several degrees of freedom 
(DOF) have been at least partially satisfied using a variety of different 
methods. In many cases six degrees of freedom must be imparted to an 
object, however, the performance available with existing systems having 
this number of degrees of freedom is limited in some ways. 
Generally in sensitive systems the operator controls the position or 
velocity of the slave device by moving the teleoperated master or joystick 
and the joystick exerts forces on the operators hand that are proportional 
to those exerted by the slave. 
There has been significant work done in developing such devices. However, 
serial kinematic mechanisms used in conventional robotic technology are 
inadequate due to their large and varying inertias, friction and backlash. 
Mechanical devices with parallel actuation such as Stewart platforms (that 
employ parallel prismatic actuation and that are used for example in 
aircraft simulators) are some of the more promising fine-motion devices 
that essentially must trade off workspace for sensitivity of operation. 
Stewart platforms also have relatively complicated mechanical structure 
requiring many joints and have varying inertial parameters and usually a 
rather inhomogeneous force envelope, i.e. the resultant of leg forces is 
much higher in a particular direction than in others. If direct drive 
actuators are used in the legs of a Stewart platform, e.g. electric, 
hydraulic or pneumatic, each imparts different drawbacks and all result in 
a relatively expensive system. 
Some of the most promising fine-motion technology employs electro dynamic 
or Lorentz magnetic levitation (maglev.). This technology provides six DOF 
frictionless motion with programmable compliance and has been used as a 
magnetically levitated robot wrist as well as a teleoperation master in a 
very highly sophisticated application for nano-telerobotic manipulation 
systems driving a scanning, tunnelling microscope in order to `feel 
atoms`. The device used incorporated a floater actuated by six flat coils 
operating in strong magnetic fields generated by NdFeB magnets attached to 
a stator. Controlled movement of the floater relative to the stator, 
programmable stiffness, as well as commanded forces and torques are 
achieved through optical sensing and digital feedback control of the coil 
current. These maglev devices are very suitable for fine-manipulation 
tasks but are limited to a very small range of motion; by their inability 
to provide high forces for long periods of time; and by their high cost. 
BRIEF DESCRIPTION OF THE PRESENT INVENTION 
It is the main object of the present invention to provide a new mounting 
system for a platform or floater having a preselected number of degrees of 
freedom and wherein movement of the platform may be regulated and/or the 
forces applied to or by the floater may be accurately defined or 
monitored. 
It is another object of the invention to provide an actuation system to 
influence the movement of the platform in selected ways. 
Broadly the present invention relates to a mounting system for a platform 
means comprising at least one bellows means acting on said platform means 
for each degree of freedom of movement of said platform means, each of 
said bellows means being expandable, contractible and deformable without 
permitting rotation about its longitudinal axis so that said bellows means 
may be expanded and contracted axially and curved in direction deviating 
from its respective longitudinal axis without rotation about its 
longitudinal axis. 
Preferably each said bellows means will comprise at least one pair of 
counteracting pneumatic bellows means. 
Preferably said platform or floater will have at least three degrees of 
freedom and will be provided with at least three mutually perpendicular 
pairs of said pneumatic bellows means. 
Preferably said pneumatic bellows means of each pair will be substantially 
axially aligned when said pair is in a neutral position. 
Preferably said platform will have at least four degrees freedom wherein 
bearing means will be interposed to permit rotation of both said bellows 
means of at least one of said pairs of pneumatic bellows means about its 
respective longitudinal axis. 
In the most preferred embodiment of the present invention said platform 
will have six degrees of freedom with six pairs of pneumatic bellows means 
arranged symmetrically about said platform and wherein three of said pairs 
of pneumatic bellows means are arranged substantially parallel to a first 
plane and wherein three others of said pairs are arranged on axes 
substantially perpendicular to said plane and wherein said others are 
positioned symmetrically intermediate said first three. 
Preferably means will be provided for accurately controlling the pneumatic 
pressure within each of said pneumatic bellows means. 
In yet another preferred embodiment of the present invention means will be 
provided for sensing the position and orientation of said platform. 
Preferably means for controlling the pressure in each of said pneumatic 
bellows means of at least one of said pairs of pneumatic bellows means 
will comprise means for sensing pressure in each of the bellows means of 
said at least one of said pairs of bellows means, means for applying a 
predetermined air pressure to each of said bellows means of said at least 
one of said pairs of bellows means and means for selectively bleeding air 
applied to each pneumatic bellows means of said at least one of said pairs 
of bellow means at a selected rate to provide the desired difference in 
pressure in said bellows means of at least one of said pairs of bellows 
means.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The mounting system 10 of the present invention is formed by a platform or 
floater 12 supported from a stator 14 by pairs of opposed pneumatic 
bellows elements 16 or 16A (see FIG. 2 or 2A) which are represented in the 
various drawings by arrows with the arrows of each pair being designated 
by the same reference numeral with the subscript A and B thus in FIG. 1 
the first pair of opposed bellows 18A and 18B act along a first axis 20, 
the second pair 22A and 22B act along an axis 24 substantially 
perpendicular to the axis 20 and the third pair of bellows 26A and 26B act 
along an axis 28 substantially perpendicular to the other two axes, i.e. 
the axis 20, 24 and 28 are mutually perpendicular. 
The bellows 16A shown in FIG. 2A is contained within a sealed chamber 15 
into which pressurized air may be applied e.g. via line 17 to adjust (or 
measure) the forces applied by or to the platform by the bellows 16A. The 
bellows 16A is connected to one of the platform 12 or stator 14 by the 
housing or chamber 15 and to the other of the platform 12 or stator 14 via 
the connecting rod or shaft 19. 
Each of the bellows 18A, 18B, 22A, 22B, 26A and 26B will be similar bellows 
16 or 16A illustrated in FIGS. 2 and 2A respectively. These bellows are 
shown as corrugated and thus flexible so that they can be bent relative to 
their axis 30 in any direction as indicated by the mutually perpendicular 
arcs 32 and 34, for example to form a simulated s or z shape in 
substantially any direction and may be expanded and contracted axially as 
indicated by the arrow 36 by the application of gas, e.g. air under 
pressure into the interior of the bellow as indicated by the lines 38 and 
17. 
Internally pressurized bellows 16 is sealed throughout its length and at 
each axial end as indicated at 40 and 42 so that the pressure within the 
bellows changes the flexibility of the bellows and also tends to expand or 
contract it relative to a neutral position. Similarly the pressure outside 
the externally pressurized bellows 16A of FIG. 2A manipulates the bellows 
16A, i.e. the pressure difference between the inside and outside of the 
bellows 16 or 16A changes the size of the bellows 16 or 16A. 
It will be apparent that in a passive bellows system as will be described 
more fully hereinbelow with respect to FIG. 10 the bellows (400, 402 and 
404) need not be sealed since there need be no pressure differential 
between the inside and outside of these bellows. 
The description to follow describing systems incorporating pneumatic 
bellows (active as opposed to the passive system of FIG. 10) will refer 
primarily to the internally pressurized bellows 16 to simplify the 
description, however it is to be understood that this description is to be 
read as including as an alternative the externally pressurized bellows 16A 
and that, in some cases, it will be preferred to employ an externally 
pressurized type of bellows 16A in place of the internally pressurized 
type of bellows 16 as the externally pressurized type of bellows 16A may 
not buckle as easily. 
In some embodiments it is preferred to provide a bearing such as the 
bearing 44 as indicated schematically in FIG. 2 and FIG. 4 between the 
bellows 16 and the platform or floater 12 or between the bellows 16 and 
the stator 14 or both. It is also possible to provide a bellows with 
discreet axially extending segments and to interpose bearings between 
these segments to permit relative rotation of an adjacent pair of segments 
about the longitudinal axis of the bellows 16. Obviously care must be 
taken to ensure the desired pressure may be maintained in the segmented 
bellows. 
The illustration of FIG. 4 shows how the bellows 16 may expand and contract 
as indicated by the arrow 36 and rotate or be deflected as indicated at 32 
and 34 to permit movement of the platform 12 in the directions indicated 
by the arrows 36, 46 and 48. The bellows 16 may also rotate relative to 
the platform portion 12 substantially around the longitudinal axis 30 of 
the bellows 16 (i.e. about the axis 30 at its intersection with the 
platform portion 12) on bearings 44 as indicated by the arrows 50. 
Referring back to FIG. 1 and bearing in mind that each of the bellows 16 of 
the pairs of bellows 18, 22 and 26 are constructed to incorporate the 
movement described hereinabove. It will be apparent that the platform or 
floater 12 can be moved to the left, to the right, and up and down or any 
combination of such directions. It will further be apparent that by 
controlling the pressure in each of the bellows 16 the bellows can impart 
the desired movement to the platform 12 adjusting its position and 
orientation relative to the stator 14. The FIG. 3 arrangement as will be 
described below also permits or may impart movement around the axis 20 as 
indicated by the arrows 52. 
It will further be apparent that if only one pair of bellows is used, say 
the pair of bellows 18 (bellows 18A and 18B) then movement of a single 
degree of freedom is obtainable or if two perpendicular pairs of bellows 
such as 18 and 22 are used, movement of two degrees of freedom of platform 
or floater 12 along the axis 20 and 24 is obtainable. 
Referring to FIG. 3, like parts have been indicated with like reference 
numerals, however in this embodiment the bellows 18A and 18B are provided 
with bearings 44 to permit the platform or floater 12 to rotate around the 
axis 20 as indicated by arrow 52 (it being apparent that the axis 20 may 
have a jog in it due to deflection of the bellows 18A and 18B). 
To control (or monitor) this rotational movement of the platform 12 around 
the axis 20 as indicated by the arrow 52 the single pair of bellows 26A 
and 26B have been replaced by two pairs of bellows which in this case are 
spaced on either side of the axis 20 and are indicated by the arrows 26A1, 
26B1, 26A2, 26B2. 
FIG. 5 shows a preferred arrangement of the present invention offering six 
degrees of freedom for the platform or floater 100 which may take the form 
of a wrist joint or the like of a robot and to which other components may 
be fixed for example via the bolts 102. The stator 104 provides the other 
side of the wrist joint. 
In this arrangement the floater or platform 100 is mounted on the stator 
104 by the pneumatic bellows acting on a first set of lugs 106, 108 and 
110 and a second set of lugs 124, 126 and 128. The first set of lugs 106, 
108 and 110 are symmetrically positioned around the z axis i.e. spaced at 
120 degree intervals around the z axis and the second set of lugs 124, 126 
and 128 are symmetrically positioned between the lugs 106, 108 and 110 
i.e. also at 120 degree intervals around the z axis and each equally 
spaced from its respective adjacent lugs of the first set of lugs. 
The lugs 106, 108, and 110 are acted upon by opposed pairs of bellows 112A, 
112B, 114A, 114B, and 116A and 116B respectively to apply forces along 
axes 118, 120 and 122 respectively all of which are substantially 
perpendicular to, i.e. they are in a plane substantially perpendicular to, 
the Z axis. 
The lugs 124, 126 and 128 are acted on by pairs of opposed bellows 130A and 
130B, 132A and 132B and 134A and 134B respectively to apply forces along 
axis 136, 138 and 140 all of which are substantially parallel to the z 
axis. 
Each of the bellows of the pairs of bellows 112, 114, 116 and 130, 132 and 
134 are provided with bearings equivalent to the bearings 44 so that 
rotation around each of the axes 118, 120, 122, 136, 138 and 140 can also 
be obtained. This arrangement permits movement of the base 100 with 6 
degrees of freedom, i.e. movement in the x, y, z axes and in the pitch and 
yaw directions can be accommodated through the bellows mountings. This 
action or motion can be controlled by controlling the pressure in each of 
the pneumatic bellows in each of the pairs of bellows as will be described 
hereinbelow. 
The embodiment shown in FIG. 6 is essentially the same as that shown in 
FIG. 5, however instead of the bolts 102 there is provided a hand grip 
150. The corresponding elements have been indicated by like reference 
numerals in FIGS. 5 and 6. 
It will be apparent with the FIG. 6 embodiment, movement of the joystick or 
hand controller 150 has the same six degrees of freedom as in the FIG. 5 
embodiment and may be used as a control by sensing the position of the 
hand controller and as another example to provide force feedback by 
controlling pressures in the opposing pairs of bellows. 
FIG. 7 shows one system for monitoring and controlling the pressure (and 
flow) in each bellows of a pair of opposed bellows. The bellows A and B 
apply pressure along the axis D against opposite sides of the plate or 
platform 200 which is used to represent the opposed sides of the platform 
12 of the FIGS. 1 and 2 embodiments or the various flanges or lugs 106, 
108, 110 and 124, 126 and 128 of the FIGS. 5 and 6 embodiments. 
As shown in FIG. 7 bellows A and B provide or apply pressure between the 
stator or fixed element 206 and the opposed faces 202 and 204 respectively 
of the platform 200. The bellows A and B are both supplied with pneumatic 
pressure from the pressure source Ps via essentially the same circuit 
elements of which have been numbered with the same number followed by the 
A for bellows A and the B for bellows B. As indicated, pressure from the 
source Ps passes via line 208 through a fixed orifice 210 into the bellows 
A or B. The pressure in the line 208 between the fixed orifice 210 and the 
respective bellows A (or B) is sensed by the pressure sensor 212. A branch 
or bleed line 214 extends from the section of line 208 between the bellows 
A (or B) and the orifice 210 to an orifice 216 the outflow from which is 
controlled by a moving coil actuator 218 that is controllably oscillated 
or positioned relative to its respective nozzle 216 to define the pressure 
in the line 208 (A or B respectively). In a pneumatic control system of 
the type described it will be apparent that other pressure control systems 
may be used, for example a Jet Pipe valve could easily be applied. 
It will be apparent that with this system the pressure in the bellows A and 
B may be set as desired depending on the bleed through the nozzles 216A or 
216B respectively which is in turn controlled by the moving coil actuator 
218A or 218B. 
It will be apparent that other means for controlling the pressures in the 
bellows A and B may be used. 
A variety of different techniques for sensing the position of the platform 
12, 100 or 200 may be used however a preferred system is shown in FIG. 8. 
In this arrangement a light source 300 is fixed to the platform or floater 
12, 100 or 200. In the illustrated arrangement, 3 light emitting diodes 
302, 304 and 306 are provided each directing a beam of light along its 
respective axis 302A, 304A and 306A onto its respective positioning sensor 
302B, 304B, 306B which may take the form of position sensing photo diodes 
or close coupled devices (CCD arrays) that are attached to the stator 14, 
104 or 206 and are adapted to sense the location at which the beam 
projected along the axis 302A, 304A and 306A intersect the photo diodes so 
that position of the floater or platform 12, 100 or 200 can be determined 
via the cartesian coordinates of the point of contact of the light beams 
302A, 304A and 306A with their respective position sensing photo diodes. 
The simplest manner in which this may be done is to project the beams 
302A, 306A as orthogonal beams of light engaging two dimensional position 
sensing diodes and utilizing simple kinematic calculations (intersection 
of 3 spheres) to generate the position and orientation of the platform or 
floater 12, 100 or 200 with respect to the stator 14, 104 or 206. 
One technique for operating the system illustrated in FIG. 9 incorporates a 
processor 350 that receives input from the pressure sensing electronics 
352 (which senses the pressure from the pressure sensors 212A and 212B for 
each of the pairs of bellows used in the system, i.e. depending on the 
number of degrees of freedom to provide feedback of the actual pressures 
in each of the bellows A and B of each of the pairs bellows used in the 
particular mounting system being controlled, i.e. for the six degrees of 
freedom device shown in FIGS. 5 and 6 the various pairs of bellows 112, 
114, 116, 130, 132 and 134 A and B would be sensed and this information 
delivered to the processor or computer 350). 
It will be apparent that by controlling the pressure in the respective 
bellows force control may be achieved. It is possible to, for example, 
sense the pressures applied to an arm being controlled and to develop 
corresponding pressures resisting movement of a control joystick in these 
respective directions to provide a feed back to the joystick of the 
pressures or forces being encountered by the arm being controlled. 
If an optical sensor such as the optical sensor 300 (302A, 304A, 306A, 
302B, 304B, 306B) shown in FIG. 8 were also incorporated in the device, 
then the output or the optical sensed position and orientation would be 
determined as indicated at 354 and this information fed to the computer 
350. The processor 350 could also be programmed to obtain a selected 
movement of the floater 12, 100 or 200 (assuming the floater movement is 
intended to be controlled and manipulated as a wrist of a robot for 
example). 
Referring now to FIG. 10 it will be apparent that the position sensing 
system employed in this arrangement is essentially the same as that shown 
in FIG. 8, however in this system the light beams 302A, 304A and 306A 
extend substantially axially of their respective bellow 400, 402, 404 onto 
their respective detectors 302B, 304B and 306B. 
The system shown in FIG. 10 is a passive system wherein the construction of 
the bellows generates forces or stresses when the joystick and bellows are 
moved from their natural rest positions neutral and these stresses are 
absorbed by the bellows structure and function to urge the joystick and 
bellows back to their neutral positions whenever they have been moved 
therefrom and then released. 
The passive mounting system of FIG. 10 differs from the above described 
active systems in the construction of each of the bellows 400, 402 and 404 
which is such that when the joystick 406 is in neutral position all of the 
bellows are also in a stable or neutral position. Movement of the joystick 
406 in the 3 degrees of freedom provided by the three bellows 400, 402 and 
404 (one for each degree of freedom) causes expansion and/or contraction 
of each of the bellows and/or deflection relative to its longitudinal axis 
(as represented by the beams 302A, 304A and 306A respectively as described 
above. Pneumatic pressure is not required nor is it necessary to employ 
pairs or opposing bellows as described hereinabove since each of the 
bellows 400, 402, 404 has a stable position from which it may be either 
extended or contracted or bowed, but to which it always tends to return. 
The bellows 400, 402, 404 are constructed to prevent rotation about their 
respective longitudinal axis 302A, 304A and 306A so movement of the 
joystick is confined to the x, y and z directions (or combinations 
thereof) without pivoting motion of the joystick. 
Having described the invention, modifications will be evident to those 
skilled in the art without departing from the spirit of the invention as 
defined in the appended claims.