Patent Grant
9474683
Not applicable.
Not applicable.
The present invention relates generally to vibrators, transducers, and associated apparatus, and more specifically to an improved method and apparatus for generating a vibrational stimulus to the body of a user in response to an electrical input.
The sense of feel is not typically used as a man-machine communication channel, however, it is as acute and in some instances as important as the senses of sight and sound, and can be intuitively interpreted. Tactile stimuli provide a silent and invisible, yet reliable and easily interpreted communication channel, using the human's sense of touch. Information can be transferred in various ways including force, pressure and frequency dependent mechanical stimulus. Broadly, this field is also known as haptics.
A single vibrotactile transducer can be used for a simple application such as an alert. Many human interface devices, for example a computer interface device, allow some form of haptic feedback to the user. A plurality of vibrotactile transducers can be used to provide more detailed information, such as spatial orientation of the person relative to some external reference. Using an intuitive body-referenced organization of vibrotactile stimuli, information can be communicated to a user. Such vibrotactile displays have been shown to reduce perceived workload by its ease in interpretation and intuitive nature (see for example: Rupert A H, 2000, Tactile Situation Awareness System: Proprioceptive Prostheses for Sensory Deficiencies. Aviation, Space, and Environmental Medicine, Vol. 71(9):II, p. A92-A99).
The present invention relates to a low cost actuator assembly that conveys a strong, localized vibrotactile sensation (stimulus) to the body. These devices should be small, lightweight, efficient, electrically and mechanically safe and reliable in harsh environments, and drive circuitry should be compatible with standard communication protocols to allow simple interfacing with various avionics and other systems.
The study of mechanical and/or vibrational stimuli on the human skin (body) has been ongoing for many years. Schumacher et al. U.S. Pat. No. 5,195,532 describes a diagnostic device for producing and monitoring mechanical stimulation against the skin (body) using a moving mass contactor termed a “tappet” (plunger mechanical stimulator). A bearing and shaft is used to link and guide the tappet to the skin (body) and means is provided for linear drive by an electromagnetic motor circuit, similar to that used in a moving-coil loudspeaker. The housing of the device is large and mounted to a rigid stand and support, and only the tappet makes contact with the skin (body).
The reaction force from the motion of the tappet is applied to a massive object such as the housing and the mounting arrangement. Although this device does have the potential to measure a human subject's reaction to vibratory stimulus on the skin (body), and control the velocity, displacement and extension of the tappet by measurement of acceleration, the device was developed for laboratory experiments and was not intended to provide information to a user by means of vibrational stimuli nor be implemented as a wearable device.
Various other types of vibrotactile transducers, suitable for providing a tactile stimulus to the body of a user, have been produced in the past. Prior vibrotactile transducers designs have incorporated electromagnetic devices based on a voice coil (loudspeaker or shaker) design, an electrical solenoid design, or a simple variable reluctance design. The most common approach is the use of a small motor with an eccentric mass rotating on the shaft, such as is used in pagers and cellular phones. A common shortcoming of these previous design approaches is that the transducers are rapidly damped when operated against the body—this is usually due to the mass loading of the skin (body) or the transducer mounting arrangement (for example the foam material that would surround a vibrotactile transducer if it were mounted in a seat).
Pager motors, or eccentric mass EM motors, are usually constructed with a DC motor with an eccentric mass load such as half-circular cylinder that is mounted onto the motor's shaft. The motor is designed to rotate the shaft and its off-center (eccentric) mass load at various speeds. From the conservation of angular momentum, the eccentric mass imparts momentum to the motor shaft and consequently the motor housing. The angular momentum imparted to the motor housing will depend on the mounting of the motor housing, the total mass of the motor, the mass of the eccentric rotating mass, the radius of the center of mass from the shaft and the rotational velocity. In steady state, the angular momentum imparted to the housing will result in three dimensional motion and a complex orbit that will depend on the length of the motor, the mounting geometry, the length of the shaft and center of gravity of the moving masses (see for example J. L. Meriam, Engineering Mechanics: Dynamics, SI Version, 5th Edition, 2003, Wiley). This implementation applies forces in a continually changing direction confined to a plane of rotation of the mass. Thus the resultant motion of the motor housing is three dimensional and complex. If this motion is translated to an adjacent body, we may interpret the complex vibration (and perceived vibrational stimulus) to be diffuse and a “wobble” sensation.
The rpm of the EM motor defines the tactile frequency stimulus and is typically in the range of 60-150 Hz. Typically these devices are intended to operate at a single (relatively low) frequency, and cannot be optimized for operating over the frequency range where the skin (body) of the human body is most sensitive to vibrational stimuli (see for example Verrillo R. T. (1992) “Vibration Sensation in Humans”, Music Perception, Vol 9, No 3, pp 281-302). It may be possible to increase the vibrational frequency on some EM motors by increasing the speed of the motor (for example by increasing the applied voltage to a DC motor). However, there are practical limits to this as the force imparted to the bearing increases with rotational velocity and the motor windings are designed to support a maximum current. It should also be apparent that the angular momentum and therefore the eccentric motor vibrational output also increases with rotational velocity which limits use of the device over bandwidth.
The temporal resolution of EM motors is limited by the start up (spin-up) times which can be relatively long, on the order of 100 ms or so. This is somewhat longer than the skin (body)'s temporal resolution, thus can limit data rates. If the vibrotactile feedback is combined with other sensory feedback such as visual or audio, the start-up delay has the potential of introducing disorientation. The slow response time needed to achieve a desired rotational velocity is due the acceleration and deceleration of the spinning mass—some motor control methods can address this by increasing the initial torque on turn on. It should be evident that motors with smaller eccentric masses may be easier to drive (and reduce spin-up time) however, thus far a reduced eccentric mass also results in an actuator that produces a lower vibrational amplitude.
There are two important effects associated with the practical operation of EM motors as vibrotacile transducers. Firstly the motion that is translated to an adjacent body will depend on the loading on the motor housing—from the conservation of momentum, the greater the mass loading on the motor (or transducer housing) the lower the vibrational velocity and perceived amplitude stimulus. Secondly, from the conservation of momentum, if the mass loading on the motor is changed, the torque on the motor and angular rotation rate will also change. In fact it is not possible to simultaneously and independently control output vibration level and frequency. This is obviously undesirable from a control standpoint, and in the limiting case, a highly loaded transducer would produce minimal displacement output and thus be ineffective as a tactile stimulus. In fact there have been several reports of inconsistency in results (Robert W. Lindeman, John L. Sibert, Corinna E. Lathan, Jack M. Vice, The Design and Deployment of a Wearable Vibrotactile Feedback System, Proceedings of the Eighth International Symposium on Wearable Computers (ISWC'04)) and modeling attempts to overcome this using complex mounting (Haruo Noma et al. A Study of Mounting Methods for Tactors Using an Elastic Polymer, Symposium on Haptic Interfaces for Virual Environment and Teleoperator Systems 2006). Thus depending on the mounting configuration, the displacement into skin (body) and perception of vibrational stimulus is variable in frequency and level. This is obviously undesirable from a control standpoint, and in the limit, a highly loaded transducer would also produce minimal displacement output and thus be ineffective as a tactile stimulus.
Shahoian U.S. Pat. No. 6,697,043 B1 describes a computer mouse haptic interface and transducer that uses a motor transducer. This patent teaches the use a mechanical flexure system to convert rotary force from the motor to allow a portion of the housing flexure to be linearly moved. This approach relies on a complex mechanical linkage that is both expensive to implement and at high rotational velocities prone to deleterious effects of friction. It is therefore only suited to very low frequency haptic feedback.
In prior art, Shahoian U.S. Pat. No. 6,680,729 B1 an EM motor that is connected to the housing via a compliant spring. The system makes up a two degree of freedom resonant mechanical system. The motor mass and spring systems are completely contained within a rigid housing. The movement of the motor mass in this case acts to impart an inertial force to the housing. This type of transducer configuration is known as a “shaker”. The design claims improved efficiency and the ability to be driven by a harmonic motor drive for use as a haptic force feedback computer interface. The invention does not address any loading on the housing and in fact assumes that there are no other masses or mechanical impedances acting on the exterior of the housing.
Linear “shaker” transducers are well known in prior art, for example Clamme in U.S. Pat. No. 5,973,422 describes a low frequency vibrator with a reciprocating piston mass within a low friction bearing, actuated by an electromagnetic with a magnetic spring, having a spring constant K. The ratio of K to the mass M of the reciprocating member is made to be resonant in the operating frequency range of the vibrator. Other examples of prior art “shaker” transducer designs include U.S. Pat. Nos. 3,178,512, 3,582,875 and 4,675,907.
In summary, EM motors when used as vibrotactile transducers, provide a mounting dependent vibration stimulus and a diffuse type sensation, so that the exact location of the stimulus on the body may be difficult to discern; as such, they might be adequate to provide a simple alert such as to indicate an incoming call on a cellular phone, but would not be adequate to reliably provide spatial information by means of the user detecting stimuli from various sites on the body. The prior art fails to recognize the design requirements to achieve a small, wearable vibrotactile device that provides strong, efficient vibration performance (displacement, frequency, force) when mounted against the skin (body) load of a human. This is particularly true when considering the requirement to be effective as a lightweight, wearable tactile display (e.g., multiple vibrotactile devices arranged on the body) in a high noise/vibration environment as may be found, for example, in a military helicopter. Further, the effect of damping on the transducer vibratory output due to the additional mechanical impedance coupled to the mounting has not been adequately addressed. The prior art further fails to effectively utilize an eccentric mass motor as the force generator in vibrotactile transducers or provide methods that extend the high frequency bandwidth and control the response of the transducer.
The foregoing patents reflect the current state of the art of which the present inventor is aware. Reference to, and discussion of, these patents is intended to aid in discharging Applicant's acknowledged duty of candor in disclosing information that may be relevant to the examination of claims to the present invention. However, it is respectfully submitted that none of the above-indicated patents disclose, teach, suggest, show, or otherwise render obvious, either singly or when considered in combination, the invention described and claimed herein.
The present invention provides a novel implementation of a low cost eccentric mass motor vibrotactile transducer. Preferably the eccentric mass and motor form part of the transducer actuator moving mass (mechanical contactor). The actuator moving mass is in contact with a skin (body) load. The actuator moving mass is constrained into approximately vertical motion (perpendicular to the skin (body) surface) by a spring between the actuator housing and moving mass. The rotational forces provided by an eccentric mass (EM) motor are therefore constrained into predominantly one dimensional motion that actuates perpendicularly against a skin (body) load. The actuator housing contacting face is in simultaneous contact with the skin (body) load. The body load, actuator moving mass, spring compliance and housing mass make up a moving mass resonant system. The spring compliance and system component masses can be chosen to maximize the actuator displacement while minimizing the housing motion, and tailor the transducer response to a desired level. This configuration can be implemented as a low mass wearable vibrotactile transducer or as a transducer that is mounted within a soft material such as a seat. A particular advantage of this configuration is that the moving mass motion can be made almost independent of force loading on the transducer housing.
The method and apparatus for generating a vibrational stimulus of this invention provides an improved small, low cost vibrotactile transducer to provide a strong tactile stimulus that can be easily felt and localized by a user involved in various activities, for example flying an aircraft, playing a video game, or performing an industrial work task. Due to the high amplitude and point-like sensation of the vibrational output, the inventive vibrotactile transducer (“tactor”) can be felt and localized at various positions on the body, and can provide information to the user. The transducer itself is a small package that can easily be located against the body when installed under or on a garment, or on the seat or back of a chair. The drive electronics are compact, able to be driven by batteries, and follows conventional motor driver control techniques. The overall transducer may include interface circuitry that is compatible with digital (e.g., TTL, CMOS, or similar) drive signals typical of those from external interfaces available from computers, video game consoles, and the like.
A number of actuator drive parameters can be varied. These include vibrational amplitude, drive frequency, modulation frequency, and wave-shape. In addition single or groups of transducers can be held against the skin (body), in various spatial configurations round the body, and activated singly or in groups to convey specific sensations to the user.
It is therefore an object of the present invention to provide a new and improved method and apparatus for generating a vibrational stimulus to the body of a user.
It is another object of the present invention to provide a new and improved low cost vibrotactile transducer and associated drive controller electronics.
A further object or feature of the present invention is a new and improved transducer that can easily be located against the body when installed under or on a garment, or on the seat or back of a chair.
Other novel features which are characteristic of the invention, as to organization and method of operation, together with further objects and advantages thereof will be better understood from the following description considered in connection with the accompanying drawings, in which preferred embodiments of the invention are illustrated by way of example. It is to be expressly understood, however, that the drawings are for illustration and description only and are not intended as a definition of the limits of the invention. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming part of this disclosure. The invention resides not in any one of these features taken alone, but rather in the particular combination of all of its structures for the functions specified.
There has thus been broadly outlined the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form additional subject matter of the claims appended hereto. Those skilled in the art will appreciate that the conception upon which this disclosure is based readily may be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.
Further, the purpose of the Abstract is to enable the U.S. Patent and Trademark Office and the public generally, and especially the scientists, engineers and practitioners in the art who are not familiar with patent or legal terms or phraseology, to determine quickly from a cursory inspection the nature and essence of the technical disclosure of the application. The Abstract is neither intended to define the invention of this application, which is measured by the claims, nor is it intended to be limiting as to the scope of the invention in any way.
Certain terminology and derivations thereof may be used in the following description for convenience in reference only, and will not be limiting. For example, words such as “upward,” “downward,” “left,” and “right” would refer to directions in the drawings to which reference is made unless otherwise stated. Similarly, words such as “inward” and “outward” would refer to directions toward and away from, respectively, the geometric center of a device or area and designated parts thereof. References in the singular tense include the plural, and vice versa, unless otherwise noted. Further the following description may describe any combination of spring and/or bearing as a suspension mechanism.
The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein:
Referring to
An eccentric mass motor or pager motor 10 is used as the force actuator in the transducer. The motor 10 is mounted on the contactor 22. The contactor 22 is a moving element and actuates upon the body of the user 24 (usually a skin (body) load). The motor 10 may be preferentially mounted within an opening in a contactor 22. The contactor 22 is coupled to the vibrotactile transducer housing walls 21 via a set of compliant springs 23a and 23b. The spring 23 compliance are specially chosen, usually to be resonant with the mass elements in the system (including the mechanical impedance elements contributed by the body load 24). The spring 23 elements are also chosen to have characteristics that constrain the motion of the contactor 22 to predominantly vertical displacement i.e. the lateral compliance is much lower than the vertical spring compliance. These characteristics can, for example, be achieved by a pair of disc shaped planar springs described hereinafter.
Preferably the front contacting face of the housing 28 and the mechanical contactor 22 are held in simultaneous contact with the user's skin (body) 24. The mechanical contactor 22 is designed to be the predominant moving mass in the system, conducting vibratory motion perpendicular to the skin (body) and consequently applying a vibrotactile stimulus into a skin (body) load. The housing 21 and housing contacting face 28 are allowed to vibrate at a reduced level and substantially out of phase with the mechanical contactor as described hereinafter. To account for the elasticity of the skin (body) 24 and/or the layers of clothing between the tactor and the skin (body), the contactor 22, in its rest position, is raised slightly above the front surface 28 of the housing 38. The height of the contactor 22 relative to the housing contacting surface 28, and the compliance of the springs are chosen so that when the housing and contactor is pressed against the skin (body) of the user, the contactor and EM motor 10 assembly are displaced with respect to the housing to simultaneously pre-load the contactor against the skin (body) and the contactor/EM motor assembly against the action of the spring. Preferably the height of the contactor 22 relative to the front surface 28 should be about 1 mm for appropriate bias preload into the skin (body) or typical skin (body) combined with intermediate layers of clothing or covering material.
In designing a practical wearable vibrotactile device 20, the overall mass of the transducer must be small, preferably less than 50 g. This requirement includes the mass of the mechanical contactor, motor components and housing. The housing should be robust and should facilitate mounting onto a belt, seat, clothes and the like.
A description of a transduction model for the dual moving mass vibrotactile device 20 is shown in the “free-body diagram” of
The motor in the vibrotactile device 35 rotates at ω rad/s and acts on the eccentric load mass Mr 30 and produces a reaction force into the mechanical contactor mass Mc 31. This EM motor is the actuator or force driver for the system. The mechanical contactor mass 31 is the total moving mass including the mass of the motor housing, mechanical contactor and assembly. The eccentric load mass 30 is unconstrained in the system and is free to rotate. The mechanical contactor mass 31 acts upon the skin (body) or body load through lumped mechanical impedance Z1 and the housing mass 33 via a spring compliance Cs 34. The housing mass 33 also acts on a skin (body) or body lumped mechanical impedance load represented by Z2. Numerical values for the skin (body) impedance components can be found in E. K. Franke, Mechanical Impedance Measurements of the Human Body Surface, Air Force Technical Report No. 6469, Wright-Patterson Air Force Base, Dayton, Ohio, and T. J. Moore, et al, Measurement of Specific Mechanical Impedance of the Skin, J. Acoust. Soc. Am., Vol. 52, No. 2 (Part 2), 1972. These references show that skin (body) tissue has the mechanical input impedance of a fluid-like inertial mass, a spring-like restoring force and a viscous frictional resistance. The numerical magnitude of each component in the skin (body) impedance depends on the area of the mechanical contactor or housing contacting face and, as can be expected, the resistive loading of the skin (body) is shown to increase with increasing mechanical contactor (or housing contacting face) diameter.
In
The equations of motion for this mechanical circuit can be solved using well known electro-acoustic analogous circuit design techniques. A skin (body)-like load impedance is assumed to be acting on both the housing Zh, and the contactor Zc (Z2 and Z1 respectively) Thus complex mechanical properties of the skin (body), complete mechanical vibrotactile system components and motional parameters are described with this set of equations. Analysis of this system of equations is usually by direct mathematical analysis or using a computer-based equation solver. The results of such a simulation are shown in figures hereinafter.
The sensitivity of the bodies skin (body) receptors to vibrational displacement is well known (see for example Bolanowski, S., Gescheider, G., Verrillo, R., and Checkosky, C. (1988). “Four channels mediate the mechanical aspects of touch”, J. Acoust. Soc. Am., 84(5), 1680-1694, and; Bolanowski, S., Gescheider, G., and Verrillo, R. (1994). “Hairy skin: psychophysical channels and their physiological substrates”, Somatosensory and Motor Research, 11(3), 279-290.). Three receptor systems thought to contribute to detection of vibrotactile stimuli at threshold under normal conditions—Pacinian corpuscles (Pc), Meissner's corpuscles, and Merkel's disks. Of these, the Pacinian corpuscles are the most sensitive. At 250 Hz, the sensitivity of the human skin (body) to displacement is less than 1 μm (Pc).
Mechanotransduction is the process by which displacement is converted into action potentials. Pc receptors are located relatively deeply within the skin (body) structure. In this range, the human perception of vibration depends primarily on mechanical contactor displacement, and is most sensitive to displacement that is normal to the skin (body) surface (as opposed to tangential or shear). Pc receptors also show an effect known as special summation where there is a reduction in detection threshold as a function of the contact area. Such a mechanism has been explained as the addition of energy from larger and larger areas of stimulation.
If we define the “skin (body) stimulus” to be the product of the mechanical contactor area and the relative mechanical contactor displacement, we can solve the equations of motion for the system at 250 Hz and 100 Hz and plot “skin (body) stimulus” against various diameters of contactor in cm (keeping the other parameters constant). This function, shown in
The springs 23 serve as a suspension mechanism to position the motor and mechanical contactor assembly concentric to the housing assembly, and provide a controlled mechanical compliance in the perpendicular direction (direction of motion) so that when the mechanical contactor and housing is pressed against the skin (body) of the user, the mechanical contactor is displaced with respect to the housing to simultaneously pre-load the mechanical contactor against the skin (body) and the contactor/motor assembly against the action of the spring. The compliance of the spring in the perpendicular direction also serves to set the mechanical resonance frequency of the transducer when applied to the skin (body), as described previously. The circular planar spring also serves to constrain the displacement of the mechanical contactor (including the EM motor) to the perpendicular direction.
The drive signal depends on the motor 10 design, but is typically a DC voltage. A particular problem with DC motors is the start up characteristics and consequently slow rise time. This can be reduced in part using pre-compensated drive voltage waveforms—increasing the voltage and motor torque at start up. An alternative approach is to keep the motor 10 rotating at slow angular velocity at periods when the vibrotactor transducer system 20 is intended to be off. This has the effect of avoiding motor startup delays and the effects of stiction in the mechanical system. Operating the vibrotactile transducer at low frequencies can be designed to cause a vibrational stimulus to be applied to a person's body which is below the threshold for detection. For example,
The selection of EM motor 10, housing contacting face area 100, housing mass, mechanical contactor 22 area, contactor mass and suspension spring compliance 23 again follows the analysis of the free body diagram described in
In some applications, an elongated mechanical contactor 106 can also be extended beyond the housing 21 front face 100 such that the contactor is in close proximity to the skin (body) load 24. This is beneficial in situations where the thickness of the intermediate foam material 104 needs to be minimized to increase the perception of the tactile stimulus. This embodiment of the invention is shown in
FRadial=MErEω2
Where ME is the eccentric mass, rE is the radius to the COG of the eccentric mass and ω is the angular frequency determined by the motor rotation. This well known relationship demonstrates how an EM motor produces an inertial force proportional to the size of the eccentric mass and the rotational velocity squared. It also shows why the force or displacement output is not constant with frequency. Note that the eccentric mass inertial is more difficult to rotate at higher rpm. Larger motors driving a large eccentric mass ME loads can be used to actuate with a reasonable force at lower angular frequencies while smaller motors driving a relatively small eccentric mass load ME(2) can be used at correspondingly higher frequencies—the combination of the two or more EM motors (and loads that are sized appropriately) can therefore be designed to actuate with approximately constant force across a wide range of operating angular frequencies. A controller 111a consists of a means for controlling multiple EM motors, individually or in combination. Said controller may also include a means for measuring the mechanical contactor displacement and using this as a feedback input variable for the controller. The compliance of springs 23, contactor mass (11) and housing mass (21) can be sized in accordance with the load impedance (usually a skin (body) load and skin (body) mechanical impedance) as described hereinbefore and the desired output vibratory characteristics.
In another example 107b, the phase rotation θ1 and θ2 of similar EM motors 10c and 10d can be synchronized to obtain a cumulative effect. Both motors are mounted on the same axis 110. The phase of each of the masses is orientated using a motor controller 111b. For maximum vertical displacement (i.e. on axis with the contactor), each of the motors should be driven at the same rotational rpm, the eccentric masses simultaneously reaching the vertical axis but the rotational directions being opposite for each motor. This arrangement cancels the lateral displacement of the contactor 22 and produces cumulative vertical vibration. This is desirable as the vibratory output will be perpendicular to an adjacent skin (body) load (not shown) and also provide less lateral forces on the spring component 23.
Accordingly, the invention may be characterized as a vibrotactile transducer to provide a vibrational stimulus to the body of a user in response to an electrical input, including a housing having a contacting face, the contacting face having an opening; a mechanical contactor; suspension means including at least one spring for suspending the mechanical contactor in the housing and constraining the motion of the mechanical contactor in the housing; and at least one eccentric mass motor attached to the mechanical contactor, wherein when an electrical control input is applied to the eccentric mass motor, the inertial forces from the eccentric mass motor causes the mechanical contactor to vibrate between a refracted position within the housing and an extended position through the opening.
The mechanical contactor is preferably separated from the opening by a radial gap, and may have a diameter of between 0.9 cm and 3 cm. The suspension means preferably constrains motion of the mechanical contactor to predominantly perpendicular motion with respect to the contacting face. The suspension means may include at least one leaf spring, at least one spiral spring, or a combination thereof, and may further include a linear bearing. The compliance of the spring is preferably chosen to be resonant with the mass of the housing, the mechanical contactor, and the body mechanical load. The compliance of the spring preferably magnifies the displacement of the mechanical contactor. The at least one eccentric mass motor may include multiple eccentric mass motors attached to the mechanical contactor to produce various effects, which may be synchronized to sequence the combined mechanical contactor and eccentric mass motor motion, or may include at least two differently sized eccentric mass motors, and a controller that preferentially selects the relative usage of the eccentric mass motors, the combinational output offering control of the overall vibrotactile transducer force vs. frequency output of the system. The contacting face may have a mass and area such that it acts as a reciprocating mass in a seat mounted transducer or a wearable transducer.
Alternatively, the invention may be characterized as a method for providing a vibrational stimulus to the body of a user in response to an electrical input, the method comprising the steps of providing a vibrotactile transducer in the form of a housing having a contacting face with an opening, a mechanical contactor, and spring means for suspending the mechanical contactor in the housing so that the mechanical contactor can extend through the opening; attaching at least one eccentric mass motor to the mechanical contactor; pressing the contacting face against the body of a user so that the contacting face and the mechanical contactor are initially in simultaneous contact with the body of the user; and actuating the at least one eccentric mass motor to deliver a vibrational stimulus to the body of the user.
The inventive method may further include the step of suspending the mechanical contactor within the housing to constrain the motion of the mechanical contactor to a plane that is normal to the contacting face, controlling the resonance of the mechanical transducer within the band 50-300 Hz, mounting the vibrotactile transducer within a seat, continuously rotating the at least one eccentric mass motor at low rpm in off periods to avoid start-up delays, or synchronizing multiple eccentric mass motors to sequence the combined mechanical contactor and eccentric mass motor motion.
In some embodiments, suspension 527 elements may be constructed using an elastomeric material, for example silicone rubber, or thermoset rubber polymer and the like. In certain embodiments it is preferable to pre-stretch the elastomeric suspension element 527 to hold it in tension—this may be accomplished by manufacturing the elastomeric suspension element 527 with a shorter length than the distance from the housing wall 536 to the contactor 522, thereby stretching the suspension element during assembly, and providing an initial preload to the contactor. Suspension 527 elements may in some embodiments protrude through the housing wall 536, having a thicker portion 529, or plug, exterior to the housing 536, thereby acting as an attachment point 532.
At rest in an unloaded transducer configuration, the contactor 522 protrudes through opening 525 or radial gap.
In the unloaded vibrotactile transducers rest state shown in
The eccentric mass (EM) motor 510 is connected to a suitable external power source and controller electronics which causes the motor shaft and eccentric mass load to rotate. As described hereinbefore, from the conservation of angular momentum, and the centering action of one or more spring components 527, the mechanical contactor 522 moves about its initial position. For the unloaded vibrotactile configuration shown in
The rear of the transducer 537 may in certain embodiments, be left open. In this case, the rear of the transducer 537 will not have a cover and must be mounted in configurations where external objects do not present additional loading or disrupt the operation of the internal (moving) components.
In certain embodiments it is preferable to pre-stretch the elastomeric suspension elements 558 by manufacturing the elastomeric suspension elements 558 with a shorter length than the distance from the housing wall 553 to the motor housing 552, thereby stretching the suspension element during assembly. Suspension 558 elements may in some embodiments protrude through an opening 559 in the housing wall 553, the suspension elements having a thicker portion 555, or plug, on the exterior of the housing. The rear of the vibrotactile actuator housing 557 may include a cover or in other embodiments, be omitted so that the housing is essentially reduced to a ring to which the suspension elements 588 attach.
In certain embodiments of this invention, it is preferable to design the motor housing 552 to fully enclose the one or more eccentric mass motors, thereby making a water proof vibrotactile transducer configuration. A water resistant, electrical wire pass-through can be constructed into the wall of the motor housing 552 to establish electrical control connections to the eccentric mass motor(s). In such designs, sufficient clearance to accommodate the eccentric mass rotation must be provided within the motor housing 552. In other embodiments, deeper immersion (i.e. functional in water to greater depths) can be achieved by fully enclosing the motor housing 552 and filling the interior cavity with a low-viscosity oil (for example 100 centistoke electrical grade silicone oil). Generally the oil volume should be as low as possible so as to avoid substantial increases to the moving mass in the vibrotactile transducer. In other “covert” or low acoustic emission embodiments, it is preferable to design the motor housing 552 so as to fully enclose one or more eccentric mass motors, and fill the volume surrounding the eccentric mass with a low viscosity fluid. The fluid has the benefit of damping structural vibration and therefore reduces the noise level produced by the transducer during operation. In other examples, oil filling the electrical motors and housing can increase the heat transfer from the interior motor coils, provide motor component lubrication and can therefore improve the performance of the motors.
In some embodiments, suspension element attachment points 589 and 588 corresponding to suspension elements 576 and 578, may be moved closer to the edge 598 of the motor housing. This may be effective in reducing lateral vibration (or wobble) and enhancing vibration perpendicular to the plane of the contacting face.
It should be evident from the foregoing discussion that there are a multitude of potential suspension configurations that can be used in this invention. Each of the configurations described uses symmetry in the positioning of the suspension elements to advantageously restrict the potential vibration of the moving elements of the vibrotactile actuator (the eccentric mass motor, the motor housing and the contactor) to motions that are predominantly vertical (i.e., perpendicular to the plane of the attachment of the suspension elements and containing the motor axis of rotation, and also perpendicular to the plane of the contacting face). Other configurations using multiple suspension elements are envisioned including two (preferably wide) suspension elements; the three, four and six suspension element embodiments discussed above; and, in the limit, the suspension element may be a continuous membrane suspending the contactor in the housing. It should also be evident from the foregoing discussion that multiple suspension elements may in some embodiments be designed with different lengths, thicknesses and shapes.
Driving multiple small eccentric mass DC motors in parallel (with appropriate wiring polarity) can result in the system self-synchronizing. Thus the system is naturally coupled and vibrates with both eccentric mass motors achieving the same frequency and eccentric mass rotation phase. The motors must be positioned symmetrically (as in the embodiments described hereinbefore) and the suspension elements must be symmetrical.
The housing 607 may be substantially cylindrical, or, in other embodiments, the housing 607 may be non-cylindrical, for example the housing may be elongated to accommodate one or more larger length eccentric motor components (for example 613 and 614 or 617 and 618).
The above disclosure is sufficient to enable one of ordinary skill in the art to practice the invention, and provides the best mode of practicing the invention presently contemplated by the inventor. While there is provided herein a full and complete disclosure of the preferred embodiments of this invention, it is not desired to limit the invention to the exact construction, dimensional relationships, and operation shown and described. Various modifications, alternative constructions, changes and equivalents will readily occur to those skilled in the art and may be employed, as suitable, without departing from the true spirit and scope of the invention. Such changes might involve alternative materials, components, structural arrangements, sizes, shapes, forms, functions, operational features or the like. Therefore, the above description and illustrations should not be construed as limiting the scope of the invention, which is defined by the appended claims.
The present application is a continuation-in-part of application Ser. No. 11/787,275, filed Apr. 16, 2007, and now issued as U.S. Pat. No. 8,398,569, issued Mar. 19, 2013, and which claimed the benefit of the filing date of U.S. Provisional Patent Application Ser. No. 60/792,248, filed Apr. 14, 2006. The foregoing applications are incorporated by reference in their entirety as if fully set forth herein.
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