Abstract:
A single-axis or multi-axis joystick assembly which is operative with a minimal amount of input force or displacement. As such, the joystick assembly is especially suited for those with severe motor handicaps who have limited movement in their extremities. The joystick assembly includes a housing and a handle operatively mounted to the housing for movement relative thereto. The handle operatively engages a sensor which generates an output signal when an input force is applied to the handle. The output signal is proportional to the input force. Preferably, the sensor is a piezoelectric pressure transducer.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to a joystick assembly. 
     BACKGROUND OF THE INVENTION 
     A joystick can be used in a variety of applications. For instance, a joystick may be used as a computer input device or as a mouse replacement; as a control stick for controlling the movements of mobile or stationary equipment, such as self-propelled wheelchairs for the handicapped, excavators and robots; as a slide for mixing board potentiometers; for parameter modification in machine control; and for manual entry of variable scale magnitudes. These known uses for joysticks share the common property that the greater the manually effected deflection, the greater the resulting change in the variables will be; the more rapidly the deflection must be performed, the more rapidly the variable should change. For the handicapped, who must act with the muscles in the remaining stump of an amputated extremity to control a prosthesis or a vehicle, such joysticks are difficult to operate, if at all, because the radius of action within which these persons can still exert a controlled muscle force no longer covers the stroke of such displacement-dependent joysticks. Finally, the large stroke input also requires a large amount of space for the construction and operation of these joysticks. This deficiency exists not only with potentiometer entries, but generally for displacement sensors for the generation of analog control signals, for example, in pivot lever systems for linear displacements with internal kinematic conversion. In addition, lever systems in joysticks often have the disadvantage of nonlinear reactions to the input stroke, which complicates some control tasks. Joysticks with bending elements with wire resistance strain gauges according to GB 2,211,280 A or EP 0,151,479 A or with Hall elements according to WO 93/20535 A as sensors have similar disadvantages. If the manually executed stroke is limited, the resolution, and thus the precision and reproducibility of the setting, is reduced. Moreover, such joysticks which are actuated by displacement inputs present, from a manufacturing standpoint, a solution which is quite expensive and sensitive to mechanical interference, such as, sensitivity to impact or shock. Although the latter drawback does not strictly apply to key pairs, for example, the buttons or remote volume controls of a radio receiver, the precise fine tuning of a nearly achieved specified valve is complicated even for keys reacting at two speeds, and thus is imprecise in practice. 
     SUMMARY OF INVENTION 
     The present invention provides a robust single-axis or multi-axis joystick which can be encapsulated to protect against contamination, yet remain easily accessible and resistant to impact. With this joystick, a person can enter values with great accuracy, reproducibility and dynamic response, all without becoming fatigued over a long time. Advantageously, the rest position (e.g., the null position) should be particularly easy to find from any position, and in addition implementation of the joystick should be cost effective, because it is very simple, compact and reliable. 
     The present invention is primarily a single-axis or multi-axis joystick, which can receive inputs from a user with virtually no displacement of an input handle. As such, the joystick can be used in a fatigue-free manner, with minimal use of force, so that persons with extremely severe motor impairment can use it. The core of this solution is a mechanically stable, simply designed but precise suspension of a one- or two-arm lever, preferably tared to a neutral equilibrium, which rests almost without clearance against sensors which are engageable with virtually no displacement of the lever. The lever includes a handle extending out of a sealed housing. The handle is pivotable about an axis to receive manual inputs transverse to the pivot axis. In contrast to known displacement-dependent joysticks, the joystick of the present invention operates practically without mechanical deflection and without free play. Advantageously, the pressure input direction is not unintentionally lost, as in the case of movement along a freely specifiable path in a two-axis system. This has a particularly positive effect on the control of cursor movement, for example, during CAD entry. Displacement-free joysticks can also be cascaded for very precise two-axis entry because their handles can be arranged one inside the other with low radial clearance. 
     The pressure exerted on the sensor can also be integrated by signal-processing technology as long as the pressure remains present, and for the case of a known pressure dependence of the physical sensor behavior, thus permits the implementation of pressure measurement tasks and also force measurement tasks in the case of pressure application to a constant surface area. Thus, the swing of the output signal, e.g., the path length of a linear cursor movement or the end position of a digital display device, is dependent on the duration of the pressure input, and the dynamic response of the signal, e.g., the speed of the movement of a cursor on the display screen or the rate of change of the digital display device, is dependent on the intensity of the pressure currently being manually applied, with practically no displacement, to the handle. 
     Therefore, this joystick is particularly well suited for industrial use under rough environmental conditions, for those handicapped who have limited bodily movement, and for surgeons to control motorized aids during surgery. 
     Although in the context of the present invention, the housing of the joystick is mounted rigidly with the handle projecting therefrom to receive inputs, it is within the purview of this invention that the handle be mounted rigidly and the actuation forces be inputted through a manually accessible housing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 represents a joystick assembly according to the invention with a two-arm lever and with two sensors parallel to the housing axis; 
     FIG. 2 shows a joystick assembly similar to that of FIG. 1, but with a roller bearing in its handle and with two sensors disposed radially with respect to the housing; 
     FIG. 3 represents two coaxial cascading joysticks according to those of FIG. 1; 
     FIG. 4 shows a joystick cascade according to FIG. 3 with sensor arrangement according to FIG. 2; 
     FIG. 5 shows a joystick with sensor force application according to FIG. 1, but with a one-arm handle lever; and 
     FIG. 6 shows a joystick according to FIG. 5 but with an elastic axial bracing instead of a roller bearing suspension of its handle. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     At an opening  10 , a linear rod-shaped handle  12  is held by a form-fitting suspension  11  and extends outwardly from housing  14  in each illustrated embodiment. Although only minimally pivotable under transverse force input, the handle  12  is suspended from the housing  14  in an articulad manner, specifically by means of a ball joint  18  (FIGS.  1  and  3 - 5 ), by means of a roller joint  29  (FIG. 2) or by means of a resilient block  28  (FIG.  6 ), and, more specifically, suspended directly or indirectly between lateral housing walls  17  (FIGS. 4,  5 ,  6 ), from a housing cover wall  16  (FIGS. 1,  2 ,  3 ,  4 ). 
     In applications requiring less precision, the geometrically defined joints  19  and  29 , which are axially rigid with respect to the handle  12 , can be replaced by rubber mounts, which are bonded, for example, by vulcanization, on all sides to the handle  12  and the housing  14 . 
     Although the handle  12  and pressure element  15  are subject to minimal displacement during force input, it has been found that using geometrically defined spherical or roller bearing of the joints  19 ,  29  yields more precision and less static friction. Because static friction is minimized, the control element has higher sensitivity and reproducibility during the application of pressure to the sensors  25 . By using this type of suspension  11 , it is possible, for example, to guarantee a response sensitivity of 200 mN for a rod having a diameter of 30 mm for the handle  12 . 
     Because the form-fitting suspension  11  provides a rigid structure for handle  12  and pressure element  15 , sensors  25  are insensitive to axial mechanical stresses on the handle  12 ; thus the electrical output, which alone determines the control function based on the manually applied transverse pressure, is not influenced by axially applied stresses. In rough machine operations or in fatiguing design work, the operator can grip the projecting handle  12  with his/her fist, and rest the fist on the housing cover plate  16 , without causing an excitation of the sensors  25 , before the fist causes a lateral application of force to the handle  12 . Because axial pressure components and tensile forces are absorbed by the precision bearing of suspension  11  in stable housing  14 , they do not cause a displacement of the pressure element  15  which subsequently applies force to the sensors  25 . 
     The convex profiled piece of the ball joint  18  can be attached to the handle  12  or molded directly to its outer surface, so that it projects radially outwardly from the handle  12 . The convex profiled piece rests in a dish  19  with a hollow spherical portion which may be, for example, secured to the housing  14 , or molded directly as a part of the housing  14 . In the case of an undivided double dish  19 , its central hole can be enlarged or expanded by temporary heating, in order to accommodate the spherical profiled piece  18  in the form of a bearing. It is also possible to design the dish  19  as a part of the housing with resilient elements in the upper half, to achieve simpler manufacturing and assembly. The seal of housing  14  with rigid suspension  11  about the fixed point of rotation relative to the axial direction of handle  12  is the essential reason for the high reproducibility and response sensitivity of the pressure application to the sensors  25 , with the possibility to adjust the external force input requirements depending on the lever arm ratio with respect to the joint  18  or  29  (particularly compared to the corresponding properties, for example, of an unstable toe bearing at the lower end of a swivelling lever handle against the bottom of the housing; or a handle which is braced at the lower end with a swivelling plate for irregular axial pressure application to a group of sensors as described in EP 0,616,298 A). 
     The ratios for a uniaxial or roller joint bearing  29  of the lever consisting of handle  12  and pressure element  15  (FIG. 5) are correspondingly advantageous if the handle  12  with its pressure element  15  is supported in housing  14  by a stationary shaft with the insertion of a sliding, spherical or other bearing  31  inside ring  35  of handle  12  (FIG.  2 ). The ring  35  is preferably surrounded by a profiled part  30  in the shape of a hollow cylinder, approximately in the adjacent wall of the housing  14 , which again results in a good sealing of the interior of the housing  14  in which the sensors  25  are arranged. 
     For this roller joint  29  (FIG.  2 ), the movement of lever  12  is restricted to pivotal motion about the axis of roller joint  29 . However, in the ball joint  18  (FIGS.  1  and  3 - 5 ) and in the resilient block  28  (FIG.  6 ), it is possible, in principle, to apply transverse pressure in any direction with respect to the housing  14  onto the handle  12 , which extends from the housing  14 , for example, terminating with a finger groove  32  (FIGS. 1,  5 ,  6 ), or equipped with a finger ring  27  (FIG.  3 ). Accordingly, depending on the arrangement of force sensors  25  in the housing  14 , preferably only in two mutually orthogonal directions (FIGS.  1  and  3 - 6 ), into which a pressure force which is acting laterally on the handle  12  is decomposed according to a force parallelogram. If no protection is provided for over rotation for ball joint holder  18 , then one can change the direction of the applied pressure about the longitudinal axis of handle  12 , and still maintain a constant resultant of the force parallelogram. This facilitates the control of the cursor during CAD input. To effect rotation of the transverse force into the handle  12 , it is necessary to equip the free end of the handle  12  with a rigid cap or dish (not shown) which can easily be gripped by the finger tips. However, should this rotation of the handle  12  be undesirable, a type of Cardan suspension consisting of two orthogonal roller bearings can be implemented for the two-dimensionally acting handle  12 . 
     In the housing  14 , pressure elements  15  are rigidly affixed to handle  12  for the transmission of force to the sensors  25 . The handle  12  and its pressure element  15 , depending on the relative position of bearing joints  18 ,  28 ,  29 , together form a two-armed (FIGS. 1-4) or a one-armed (FIGS. 5,  6 ) lever. The two-armed lever is preferably tared to neutral equilibrium by means of a longitudinally adjustable counterweight  34  (FIGS. 1-5) so that pivoting resulting from transverse pressure to the handle  12  (which in any case is quite minimal) can be introduced with greater sensitivity, and thus position-dependent pressure influences on the sensors  25  can be avoided as much as possible. 
     For a one-armed lever, the taring weight  34  lies outside the actual lever area between the handle  12  and the pressure-transferring element  15  for the sensors  25 , on the other side of joint  18  (FIG. 5) or  29 . As such, the opening  10  would have to be sealed in addition, for example, by means of a bellows sleeve. One advantage of the one-armed lever is the short axial length of the system. That is, the one-armed lever provides a compactly constructed tared freely-moving, displacement-free joystick. 
     In both cases, it is possible to specify a response pressure upon application of an input pressure to the handle  12 , by means of lever ratios, by means of elasticity constants (see below) and prestresses applied to the support bodies  26 , and finally by the response sensitivity of the sensors  25 . The instant applied pressure to the sensors  25 , individually or paired in a differential connection, can be queried by a signal-processing unit inside or outside of the housing  14 . In this embodiment, a signal swing conversion can occur as function of the duration or intensity of the instant transverse pressure application on the handle  12 . 
     The lever consisting of handle  12  and pressure element  15  extends from opening  10  between the lateral walls  17  of the tubular housing, preferably rectangular in cross section. inside housing  14 , pressure elements  15  are always parallel to, but not contacting, sensors  25 . However, under certain mechanical prestress, the pressure elements  15  are parallel (FIGS. 1 and 3) or transverse (FIGS. 2,  4 - 6 ) with respect to the axial direction of the handle  12  and contact the sensors  25 , where the sensors are mounted to the housing  14 . Each sensor  25  may be, for example, a semiconductor, a piezoelectric transducer, a magnetostrictive or light fiber element, or any other analog pressure sensor which is operable without displacement. 
     By inserting rigid disk  24  of defined surface area between the pressure element  15  and the sensor  25 , the manually transmitted pressure is converted according to the lever ratio into a force. The disk  24  simultaneously equalizes the pressure acting over the sensor surface area, which is of practical importance, for example, for the characteristic curve profile in polymer film pressure sensors. 
     An equalization of the pressure transfer onto the individual sensors  25 , while maintaining contact with the pressure transmitting element  15 , is achieved by inserting slightly elastic deformable support bodies  26  behind (FIG. 1) or in front of (FIG. 3) the sensors  25 . As such, the chance of mechanically overloading the sensors  25  is eliminated. At the same time these deformable bodies  26  effect, like elastic intermediary piece  33  between the handle  12  and pressure element  15  (FIG.  1 ), a measurable deflection when pressure is applied to the handle  12 . In certain applications, particularly in rough machine operation, it may be desirable to require increased manual intervention to effect an input. However, in accordance with principles of the present invention, it is not displacement but rather force which is the input variable. Although this control element is operable without displacement, the elastic intermediary piece  33  must not be too soft. 
     In order to apply pressure with higher precision and reproducibility despite minimal pivoting of the pressure element  15 , the pressure is applied perpendicularly onto the sensor  25  or onto a separately applied disk  24  by means of a spherical intermediate member  22 . Spherical member  22  can be formed at the disk  24  or at the pressure element  15  as a knob. If spherical member  22  concentrically surrounds pressure element  15  as a molded-on ring, then any over-rotation will not effect the actual pressure applied to the sensor  25 . 
     A pair of sensors  25  is provided diametrically opposing one another with reference to the axis of the handle  12  for each control axis of the control element. In this configuration, differential evaluation serves to, for example, linearize the effective response characteristic curve, define the quiescent point or eliminate influences not directly opposite each other, such as from thermal expansion effects or mechanical acceleration influences. 
     To reduce costs, only one sensor  25  is needed per axis; the second sensor may be a dummy  20  which is not connected to the data collection unit. The second sensor may also be an elastic bracing body ( 26 ) or a separate rigid spring  21  (FIG.  2 ). Each sensor  25  per axis, which is now the only one acquired by the data collection unit, is thus prestressed by its counterpart which is at a resting position, in order to increase or to decrease its internal pressure depending on the direction of the manual transverse force applied to the handle  12 . 
     Since the handle  12  undergoes nearly no deflection during the application of force, the handle  12  may have an outer member  50  and an inner member  52  (FIGS.  3  and  4 ), which are pivotally suspended to respective upper and lower portions  54 ,  56  of housing  14 . These outer and inner members  50 ,  52  can operate four axes simultaneously with one hand, for example. Inner member  52  is coaxially aligned with outer member  50  with some radial clearance therebetween. For both outer and inner members  50 ,  52 , the same lever ratios are maintained on both sides of their ball joints  19  from the suspension  11 , so that both outer and inner members  50 ,  52  can be operated with the same characteristic sensitivity. Preferably, both inner and outer members  50 ,  52  are equipped with a finger controlled ring  27 , in order to introduce compressive and tensile forces into the respective handles  12  without the need to grip it. Thus, two adjacent fingers of one hand can simultaneously operate inner and outer members  50 ,  52  about four axes. It will be appreciated that an additional set of concentrically mounted handles could be disposed parallel to inner and outer members  50 ,  52  in order to provide control about eight axes with a single hand. 
     The joystick of the present invention can thus be manufactured economically in a reliable embodiment and as a result of sealing the housing  14  and the sensors  25 , the joystick is largely unaffected by environmental influences. In operation, these joysticks are characterized particularly in to their bearing suspension  11  of the handles  12  by an extraordinarily high response sensitivity and by reproducible behavior during the manual application of force into the handle  12 . This provides various operational possibilities, for example, one finger could operate the handle  12  by laying it into a groove  32  (FIG. 1,  5  and  6 ) affixed to the top of handle  12 .