Patent Application
20210282943
The present invention relates to the harvesting of mechanical energy from a prosthetic foot equipped prosthetic leg during ambulation for the purpose of providing electrical energy to operate a prosthetic leg vacuum pump used for vacuum socket mounting of the residual limb. The harvested energy provides internal battery recharging for continued vacuum pump operation improving support for variations in user ambulatory activity, and reducing requirements for external battery recharging equipment.
Prosthetic legs have been needed throughout recorded history by people to maintain physical activity and address daily life needs after leg amputation. Advances in medical, mechanical, and electronics technologies applied to prosthetic inventions have enabled improvements in prosthetic leg performance, comfort, and health effects for users.
Prosthetic leg and foot variations in users include those with above knee, knee, below knee, and ankle amputations. A method for the mounting of a prosthesis to complete an amputee's working leg and foot has been to equip the prosthetic leg with a socket to receive the residual limb.
In the last 25 years, a technical improvement has been the use of a vacuum assisted (also referred to as hypobaric) socket. This has been found to improve the fit of the residual limb to the socket, which improves comfort and avoids tissue damage in use. It also has been found to improve residual limb blood circulation and tissue fluid levels, improving user health. Due to the large variation in residual limb mounting needs and user age, the vacuum assisted socket mounting method has been found to be suitable for a large number, but not all, amputees.
A drawback of the vacuum assisted socket mounting method has been the need for a source of controlled vacuum to the socket. Another drawback of the vacuum assisted socket mounting method is that the vacuum must be maintained to provide retentive force of the prosthetic to the residual limb during active use by the wearer. This has resulted in a variety of inventions using mechanical or electrical pumps to provide the necessary pressure control and evacuation of the socket.
For the methods and devices using electrically operated vacuum pumps, a battery is generally employed to provide operating power, which needs to be periodically replaced or recharged. A variety of technologies have been identified to address this need, including inductive coupling, radio frequency broadcast, direct wire connection, fluid turbine/generator combinations, and others.
A variety of inventions have been devised to harvest electrical energy from human leg motion which could be used to accomplish vacuum pump battery recharging. Ambulation causes forces and flexing across all elements of the foot and leg, with typical force durations, timing, and available energy for harvesting varying significantly. Accordingly, energy harvesting techniques used at each location vary significantly, and the availability of energy for harvesting varies by the form of limb use in ambulation. All variations of leg amputations have the prosthetic foot element in common as an available mounting location and energy harvesting source. Access to this energy can be accomplished with minimal intrusion of the prosthetic foot by using the force and movement accessible at the foot sole. Ambulation creates periodic but intermittent, discontinuous, and often relatively high values of force and movement in the foot sole which occur over a relatively short period of time. Because of the relatively short duration of high force values applied to the foot during ambulation, particularly at the heel, the form of each force and time function event is often referred to as a pulse or impulse.
A number of inventions accomplish energy harvesting at the foot sole, using various methods to convert impulsive energy to the required continuously available energy. Although these inventions are capable of harvesting energy for prosthetic equipment use, they do not meet a number of other physical requirements for many prosthetic leg users employing electrically operated vacuum pumps. An additional complication in prosthetic leg application is that although adequate mechanical energy is available for harvesting, the distribution and form of energy presented to the prosthetic varies significantly by user activity level, design of prosthetic device being used, and the specific amputation form and response of the user.
With an increasing population of prosthetic leg users, and improvements in health care resulting in increased longevity of prosthetic leg users, an overall increased demand for prosthetic leg devices which improve quality of life continues to develop. Improvements in the overall cost and performance of prosthetics is a societal challenge. Key problems in cost and quality of prosthetic devices are addressed as they are experienced by users and identified by technologists.
A problem known to be in the art with battery powered vacuum pumps is that they need either battery replacement or some means to accomplish battery recharging often on a daily basis, causing the user to experience reliability problems in the vacuum assisted socket mounting method or inconvenience in maintaining it.
Another problem known to be in the art is that harvesting energy from the impact and flexing of the foot sole requires effective response to and energy conversion of the short duration bidirectional impulsive forces which are developed in use of the prosthetic foot.
Another problem known to be in the art is that prosthetic feet are produced and applied in a variety of flexible sole element configurations to meet the needs and preferences of the user. The present variations in heel application forms include single and dual heel elements. The present variations in forefoot application forms include single, dual, and triplet forefoot elements.
Another problem known to be in the art is that a designed mechanism to harvest bidirectional force impulses often results in additional mechanical mechanisms which convert the bidirectional force impulses into stored energy and more continuous mechanical rotation to operate electric generators. The additional mechanical components add weight and mounting volume which affect the application aesthetics, user felt perceptions, and subsequently the user control abilities of the customized prosthetic.
Another problem known to be in the art is that many available technologies used to harvest, store, and control electrical energy cause additions to prosthetic component complexity and weight, adding restrictions and additional use requirements to the user with subsequent reductions in convenience and reliability.
Another problem known to be in the art is that the demanding process of accomplishing acceptable fit, form, and function for the amputee by the prosthetic clinician is complicated by the presence of additional equipment and may not be possible without reducing equipment additions to prosthetic weight, volume, and physical profile.
Another problem known to be in the art is that new prosthetic designs have improved prosthetic foot performance by dividing the physical foot into multiple support elements, more closely emulating a natural foot form. User gait patterns and support element forces are significantly affected, creating challenges to energy harvesting not addressed by many existing solutions.
Another problem known to be in the art is that existing designs for the various components used in the inherently customized prosthetic leg would require significant prosthetic component redesign or inherent incorporation in the prosthetic design.
Another problem known to be in the art is that by requiring existing design modification to an inherently customized prosthetic the addition of an optional battery charging function may not be economically feasible for an individual user.
Another problem known to be in the art is the need for external charging equipment and the need for proximity to that external charging equipment to accomplish battery recharging, which adds use restrictions and inconvenience to the user.
Another problem known to be in the art is that the recharging process often requires that the prosthetic and vacuum pump not be in use during the recharging process, adding further use restrictions and inconvenience to the user.
Another problem known to be in the art is that the status of the battery and the need for recharging or replacement may not be determined by the user without the use of a unique external device or connection.
An assembly of mechanical, electrical, and electronic components in a prosthetic foot harvests mechanical energy from the prosthetic foot sole during ambulation, stores it as electrical energy, and manages delivered energy to prosthetic leg equipment. Electrical energy is delivered to recharge the battery supplying electrical energy to a vacuum pump for a prosthetic leg residual limb mounting socket, while minimizing prosthetic equipment effects and deviations from desired form and weight. In addition, operating electrical energy is delivered to the vacuum pump while in use, as well as reporting battery status using an RF wireless link to an external user device.
It is a primary object and intent of the present invention to extend the operating service life of a battery operated vacuum assisted socket mount without requiring battery recharging using an external energy source, thereby improving the reliability to the user. Reliability is improved by extending the service time of the prosthetic leg vacuum socket residual limb mount by the addition of energy recovered from the activity of ambulation to the available vacuum pump battery energy. Reliable operation of the vacuum assisted socket mount is a priority to the user as the loss of socket mounting force results in a loss of prosthetic function, and inconvenience to the user.
It is an object and intent of the present invention to provide a mechanical and electric generator mechanism that can harvest energy from and be responsive to bidirectional foot sole force impulses and movement during normal ambulation. The bidirectional forces presented to a foot sole are a technical challenge to successful energy harvesting due to their short time duration and impulsive form.
It is an object and intent of the present invention to easily adapt to variations in prosthetic foot construction and sole element design by minimizing the number of mounting points and using common available space above the sole and below the ankle found in typical flexible prosthetic foot forms.
It is an object and intent of the present invention to achieve a mechanical and electric generator mechanism that can harvest, store, and use the available bidirectional impulsive foot sole energy and have minimal impact on the prosthetic leg's physical and mechanical design element forces, weight, and feel. By keeping the weight and force impact on the prosthesis in application as perceived by the user small, and minimizing the energy harvesting force impact on prosthetic operation, control adaption of the prosthetic by the user is improved.
It is an object and intent of the present invention to achieve a mechanical and electric generator mechanism and control means that can harvest the bidirectional impulsive foot sole energy, provide temporary energy storage, regulate operating voltage, and control battery charging while the vacuum pump is operating. Providing these functions reliably delivers improved prosthetic vacuum socket mount utility, aiding the health and convenience to the user.
It is an object and intent of the present invention to support the harvesting of energy from multiple prosthetic foot sole elements, and support the variability of foot sole element forces caused by variations in user gait in using a multiple element prosthetic foot. By using at least two separate mechanical energy harvesting paths adaption to variations in the user's gait patterns is accomplished with improved energy harvesting availability.
It is an object and intent of the present invention to improve the application of energy harvesting and control components by the prosthetic device manufacturer and application specialist by minimizing the points of contact with the existing prosthetic, not requiring any significant modification or redesign of the prosthesis, and supporting the user's need as optional installed components.
It is an object and intent of the present invention and its application methods of impulsive energy harvesting from the prosthetic foot sole to improve the cost and access to the user by using readily available component and material technologies in use in other industries. Through the advantages of competitive technology trends in component efficiency and reduced size, cost, and weight goals can be met with acceptable availability and cost.
It is an object and intent of the present invention to improve the installation process by the prosthetic application specialist and satisfy the user's aesthetic and convenience needs by having required components small enough that they can fit inside the prosthetic or natural leg physical envelope.
It is an object and intent of the present invention to minimize the impact to the user by avoiding any requirements for proximity to battery recharging equipment, and avoiding requirements for removing the prosthetic leg from use during recharging of the battery.
It is an object and intent of the present invention to provide recovered energy support for an optional RF communication function to report operating status to the user using a readily available consumer device. It is anticipated that this will address the user's needs for developing confidence in the prosthetic leg operation, allow activity planning, and increase overall confidence in prosthetic reliability.
A preferred embodiment of the present invention APPARATUS FOR PROSTHETIC LEG VACUUM UNIT BATTERY RECHARGING is here and in figures disclosed.
Referring to
Referring again to
To harvest mechanical energy from prosthetic leg use, force and movement of flexible heel element 20 is coupled to generator 16 and generator 17 using force limiting link and spring 14 and drive gear 15. Generator 16 and generator 17 convert the mechanical energy to electrical energy. In the preferred embodiment of the present invention, generator 16 and generator 17 are DC generators operating with rotation in both directions. Generator 16 and generator 17 are selected to minimize losses due to operation under the intermittent mechanical conditions and the impulsive electrical current conditions. The electrical energy is stored in electronic assembly 19, and subsequently used to provide electrical energy to battery and pump unit 18. In this manner the dependency of battery and pump unit 18 on stored battery energy alone is reduced, and the total of available energy is related to the user's level of activity in ambulation with the prosthetic leg. Further details of the circuits within the electronic assembly 19 are depicted in
Each user's prosthetic leg is a uniquely fitted device according to the physiology and needs of the user, whose amputation may be above, at, or below the knee. In each user's case the residual limb 84 portion is fitted to a surface contour conforming socket mount 85 which provides a physical interface to the prosthetic leg. It is to be appreciated that vacuum socket mount assembly 101 and battery and pump unit 18 associated with the present invention may be located in various positions along the user's prosthetic leg 100 according to the user's needs without altering the inventive concepts and principles embodied therein.
An individual user's application may or may not result in a set of components contained within the enclosed space of a three dimensional volume bounded by the natural leg boundary 86. Battery and pump unit 18 may also include external service connections for initial battery charging, adjustments and settings of the pump portion, and other service purposes according to the specific manufacturer (not shown). Battery status of battery and pump unit 18 is reported via an RF communication from electronic assembly 19 to user device 21. This allows the user to be aware and respond appropriately to prosthetic leg battery and pump unit 18 condition.
Energy is harvested from the force and deflection of prosthetic foot 13 elements, which in this depiction includes one flexible heel element 20 with an attached force limiting link and spring 14. It is to be appreciated that energy may be harvested from the force and deflection of one or more prosthetic foot 13 elements, including additional heel or forefoot elements, each equipped with force links and energy harvesting generators without altering the inventive concepts and principles embodied therein.
Referring to
Energy harvesting occurs using the force and relative movement of the mechanical mechanism mounting points of the prosthetic foot ankle 22 and the heel attachment sleeve 27 on flexible heel element 20. As the user steps and uses the prosthetic leg to support their weight, force is developed on the flexible heel element 20. Through heel attachment sleeve 27, compressive force is developed on the force limiting link and spring 14, which in turn causes movement of attached drive gear 15. Movement of attached drive gear 15 causes generator 16 and generator 17 shaft rotation through the force coupling by pinion gear 98 and pinion gear 97. Force limiting link and spring 14 provides a limit on the acceleration and peak force stresses of the drive gear 15, pinion gear 98, pinion gear 97, generator 16, and generator 17.
Flexible heel element 20 of prosthetic foot 13 has a spring characteristic, such that a force causing deflection will store energy in flexible heel element 20. When the user force on the heel is removed, compressed flexible heel element 20 causes the force limiting link and spring 14 to extend, causing the drive gear 15 to pivot, which causes a reversed rotation of generator 16 and generator 17. Generator 16 and generator 17 shaft rotation results in a voltage output and current flow in their connected circuits. Reversed generator 16 and generator 17 shaft rotation results in a reversed polarity of voltage output and reversed current flow in their connected circuits.
Those skilled in the art will recognize that the response characteristics of generator 16 and generator 17 must be appropriately matched to the magnitude and dynamics of the forces applied, and to the connected electrical circuits to develop the desired energy conversion and harvested electrical energy. The force and duration applied to prosthetic foot 13 flexible elements varies significantly, particularly at the heel. Applied force to the heel is often referred to as heel strike, which results in flexible element compression. Removal of the force results in extension of the heel flexible element. Ambulation typically produces a heel strike action with a duration range of 10 milliseconds to 150 milliseconds. The action of extension is typically longer in duration.
Those skilled in the art will recognize that using a rotating electric generator to efficiently provide energy conversion of this force impulse is a technical challenge, as the conventional rotating DC electric machines with a magnetic material armature core as a rotating element in the size range of interest of from 2 to 30 Watts continuous rating have a typical mechanical time constant on the order of 50 to 100 milliseconds. This time constant is too large to effectively accomplish energy harvesting of the short duration force impulses without adding additional mechanical components. To accomplish direct energy harvesting of the relatively short force impulses present at the foot bottom surfaces, at the power level in the range of 2 to 30 Watts average continuous rating, and responsive within the time frame of the impulses requires a generator and linkage assembly with a low value of mechanical time constant.
In order to meet the mechanical time constant and electrical load requirements, multiple electric machines can be used. This also aids in meeting mounting space requirements and production of the desired generated voltages. It is to be appreciated that the electrical generating capability of each generator may be varied according to need, use of one or two generators per harvesting input may be used, and the impedance of each generator may be selected to optimize impulse energy harvesting characteristics and efficiency. The number of harvesting circuits may be varied in design and application of the present invention without altering the inventive concepts and principles embodied therein.
The coreless armature DC electric machines in the continuous load rating range of from 2 to 30 Watts applied in the present invention, generator 16 and generator 17, have typical mechanical time constants of approximately 10 milliseconds, and are exemplary of electric machine technology which make this direct coupled application feasible by being able to respond to the short duration heel strike mechanical inputs. In addition, improved magnet technology and manufacturing techniques have significantly increased the energy density and reduced armature impedance, increasing energy harvesting efficiency while reducing physical size.
Those skilled in the art will recognize that the characteristics of force limiting link and spring 14 are important in the performance and management of generator 16 and generator 17 response to heel strike force. The force limiting link and spring 14 provides both a limit to the maximum value of applied force to drive gear 15 and some energy storage to aid in shaping the duration of generator response, and increasing the harvested energy. The force limiting link and spring 14 may consist of a form of slip clutch and spring, or force limiting may be accomplished by the spring alone.
Referring to
Those skilled in the art will recognize that flexibility to vary the amount and location of energy harvesting from the foot sole can be important in meeting an individual user's needs and gait pattern. Depending on the user's gait and movement activity, the forces and deflection between the bilateral elements and other sole elements can vary significantly. By providing energy harvesting links independently connected to each bilateral foot element, the total energy harvesting can remain more consistent despite asymmetries in foot sole element forces.
In the embodiment of
Those skilled in the art will recognize that a variation of this split heel configuration is possible by connecting two generators to each flexible heel element 88 and heel element 89, as depicted for a single flexible heel element 20 in
Referring to
Referring to
Referring to
Generator 17 is connected with reverse polarity from the connection of generator 16, such that both polarities of the half wave rectifier network within rectifier assembly and capacitors 45 are driven simultaneously to charge both capacitors 36 and 37. Capacitors 36, 37, 38, 39, and 40 are all large value capacitors for charge storage, selected to support the desired energy harvesting, in this case in the range 0.005F to 0.05F. Capacitors 36 and 37 are selected for the relatively large impulse currents produced by the generators. High energy density capacitors 38 and 39 provide the majority of charge storage. Capacitor 40 is selected to provide a lowered output impedance and also provides some additional charge storage.
Resistors 41 and 42 are used to provide some limitation of the charging impulse currents from generator 16 and generator 17 to the high energy density capacitors 38 and 39. High energy density capacitors 38 and 39 are used in this circuit to provide a large capacity with relatively low physical volume. The DC output connection from rectifier assembly and capacitors 45 is present at output terminals 43.
To manage the simplicity, cost, and size of this embodiment the rectifiers in
Those skilled in the art will further recognize that energy harvesting capacity can be further increased by the addition of switching circuits configured for voltage boosting to increase generator current. By using this approach stored energy may be maximized, and some independence from input generator relative impulse timing achieved.
Those skilled in the art will further recognize that the form of the rectifier and capacitor network of rectifier assembly and capacitors 45 are intended to accommodate multiple generator inputs and increase the available output voltage with a cascade structure. The purpose of this cascade structure is to tend to balance voltages when driven by unbalanced generator sources, and asymmetrical outputs from each generator. This imbalance occurs due to the difference in waveform timing between generator outputs during the sole element compression mode compared to the output during the extension mode.
A goal of the rectifier structure and storage capacitors is to consistently harvest available energy when the generators are mechanically driven by individual flexible sole elements. As the user walks, a sequence of force impulses is created as the artificial foot flexible elements are engaged in the sequence to produce controllable leg support forces. Individual force impulses may or may not be coincident in time, and of the same polarity. To maximize energy storage, charge storage should occur, as much as possible, for each input impulse from each generator, regardless of polarity or timing. This is generally accomplished using the cascade structure and generator polarity connections shown in
First, the use of two generators connected to the rectifier assembly and capacitors 45 as depicted in
Third, by selecting a second generator, system reliability is improved. In the event of one generator failure, energy conversion efficiency is affected and the amount of energy conversion may also be reduced. The benefit of this condition is that the energy conversion operation will still continue, and not cease as would be the case with a single generator.
Referring to
The network of resistor 61, resistor 62, and resistor 63 operate with the enable terminal 59 of buck/boost regulator 60 to create a hysteresis control function, which causes buck/boost regulator 60 to start operation at a relatively high value of input voltage, and only cease operation when the input voltage decreases to a relatively low value. The value of input voltage at which the buck/boost regulator 60 starts operation is determined by the circuit designer based on the energy requirements and program execution time of the control processor 49. The purpose of this control function of the present invention is to draw stored charge from rectifier assembly and capacitors 45 only when there is sufficient energy available to provide battery charging or RF communication functions. The purpose of the buck/boost function is to provide as wide a voltage range as possible so that the available energy storage and energy use is maximized.
Those skilled in the art will recognize that for buck/boost regulator 60 a switching regulator circuit may best help meet the overall size and efficiency requirements.
Referring to
The large capacitance provided by the rectifier assembly and capacitors 45 accumulates impulses of energy produced by the generators as electrical charge, which is conducted via link 104 to the electronic voltage regulator 46 to produce the electrical current used by the battery charging control 47 via link 107, control processor 49 via link 106, and RF communication 50 via link 105. The battery charging control 47 is connected to deliver current to the battery and pump unit 18 via link 108. When generator 16 and generator 17 are not operating mechanically in parallel, but are independent, the rectifier assembly and capacitors 45 provides a similar function to provide energy storage.
After the depletion of energy stored in rectifier assembly and capacitors 45, operation of control processor 49 starts after sufficient energy harvesting is complete and output voltage from electronic voltage regulator 46 is present. Sufficient energy harvesting is determined by the hysteresis control function within electronic voltage regulator 46. After control processor 49 starts, battery charging control 47 and RF communication 50 are controlled by software operation of the control processor 49, described in
Referring again to
Application of the present invention involves matching the flexible sole element forces and deflection, force limiting link and spring 14, outputs of generator 16 and 17, rectifier assembly and capacitors 45, battery charging control 47 and battery and pump unit 18. The battery and pump voltage must be matched with appropriate component selections through all of these elements.
In the present invention, force link ratings, link gear ratio, generator internal gear train ratio, and electronic component ratings can all be selected to meet the battery and pump unit 18 requirements. By performing energy harvesting on more than one prosthetic foot sole flexible element, not only can more energy be harvested, but energy harvesting can be done in a manner to accommodate different ambulation sequences and speeds, which typically apply force to the different foot flexible elements in differing amounts and with differing durations.
A force limiting link is selected to allow no more than what can be reliably accommodated by the gear, generator shaft, and other affected mechanical components. Due to the impulsive nature of applied force to the prosthetic foot sole, peak force values are often in excess of an order of magnitude greater than the value expected for continuous energy harvesting.
Limiting peak forces to within practical ratings for mechanical components allows a reliable design to be accomplished. This includes the maximum acceleration for rotating components, such as generator 16 and generator 17. Generators selected from motors designed for high performance servo control applications typically have high acceleration ratings and shaft peak force abilities, with corresponding armature winding and commutator current ratings. In addition, it is important to note that the mechanical response of the force link and gear system can be underdamped, and somewhat oscillatory in form. This is due to the stored energy in the flexible elements and spring, link mass, and the rotating elements moment of inertia. Active energy harvesting tends to minimize the underdamped response amplitude.
A desirable characteristic of the generators is low impedance. By keeping generator impedance low, terminal voltage is kept high under active energy harvesting conditions, and efficiency is improved. This is particularly true as force/time sole inputs become more impulsive in form, and peak generator currents are increased.
Referring to
Those skilled in the art will recognize that the battery charging control 47 operation can be enhanced by using the information from stored energy measurement from capacitor voltage line 51 in the rectifier assembly and capacitors 45 and battery voltage connection line 54 to set the charging current level using charging control level 53. Using this information the control processor 49 can be used to set the battery charging current as high as the stored energy available will support, the current energy harvesting rate will maintain, and the battery technology will allow.
The RF communication 50 provides wireless communication to a user device 21, such as a cell phone or separate receiver. RF communication 50 operates using the supplied regulated DC voltage with data provided by the control processor 49 using data communication line 56. The communicated data includes the sensed value from battery voltage connection line 54.
Referring to
Control logic operation starts as depicted in
The initial action in the energy management software after starting is to measure stored energy represented by rectifier module capacitor voltage as communicated via capacitor voltage line 51, battery voltage as communicated via battery voltage connection line 54, and communication status as communicated via data communication line 56 represented in action 71. Thereafter, logic test 72 is performed, which checks communication status for the readiness of RF communication 50. The RF communication 50 is ready for operation if the recorded time since the last RF communicated message was broadcast is greater than a fixed, pre-programmed time COMMPeriod, and the RF communication 50 internal circuits are ready to accept data.
If the RF communication 50 is ready, operation of the software proceeds to logic test 73. If not, operation of the software proceeds to logic test 75. COMMPeriod is intended to be chosen by the designer to be the minimum time between broadcast communications to external devices, such that the number of broadcast communications satisfies the need for sample data by the user and is not so frequent that the energy expended in communications decreases the energy available for prosthetic operation to an unacceptable level.
When logic test 73 is performed, the measured stored energy from action 71 is compared to a fixed, pre-programmed value CommEMIN 80. If the stored energy from action 71 is greater than CommEMIN 80, operation of the software proceeds to action 74. If the stored energy from action 71 is not greater than CommEMIN 80, operation of the software proceeds to logic test 75. The pre-programmed value CommEMIN 80, compared to the measured voltage of the energy storage capacitor 40, is intended to be chosen by the designer to be the minimum value sufficient to support the complete broadcast RF communication process and power needs of the RF communication 50.
When action 74 is performed, the control processor 49 operates to stop operation of the battery charging control 47 using enable line 52 and a charging control level 53. Continuing action 74, control processor 49 starts operation of the RF communication 50 to transmit a data message using RF communication control line 55 and data communication line 56. The data message transmitted consists of the value of battery voltage measured, which is used by the user to determine how much of the battery capacity remains. After action 74 is performed, software operation resumes with action 71. Action 74 is not complete until the complete communication operation is complete. RF communication 50 automatically reduces its energy consumption when the control processor 49 commanded communication operation is complete.
When logic test 75 is performed the measured stored energy from action 71 is compared to a fixed, pre-programmed value BattEMIN 81. The pre-programmed value BattEMIN 81, compared to the measured value of capacitor voltage line 51, is intended to be chosen by the designer to be the minimum value sufficient to support a significant value of battery charging current by battery charging control 47. If the measured value of capacitor voltage line 51 from action 71 is greater than BattEMIN 81, operation of the software proceeds to logic test 76. If not, operation of the software proceeds to logic test 78. When logic test 76 is performed, the measured battery voltage from action 71 is compared to a fixed, pre-programmed value BattVMAX 83.
If the measured battery voltage connection line 54 from action 71 is less than BattVMAX 83, operation of the software proceeds to action 77. If the measured battery voltage connection line 54 from action 71 is not less than BattVMAX 83 the control processor 49 operation continues with logic test 78. The pre-programmed value BattVMAX 83, compared to the measured battery voltage connection line 54 voltage of the battery and pump unit 18, is intended to be chosen by the designer to be the maximum value of battery voltage at full charge, such that any value of battery voltage that is lower is interpreted to mean that the battery will store charge if charging current is supplied. In the situation when the pump within battery and pump unit 18 is operating, the sensed battery voltage will be slightly lower than when the pump is not operating, allowing the battery charging control 47 to provide battery and pump unit 18 both charging and operating current.
When action 77 is performed, the control processor 49 operates to start charging of the battery by activating battery charging control 47 using enable line 52 and charging control level 53. After action 77 is performed, software operation resumes with action 71.
When logic test 78 is performed, the measured stored energy from action 71 is compared to a fixed, pre-programmed value EMIN 82. If the stored energy from action 71 is less than EMIN 82, operation of the software proceeds to action 79. If the stored energy from action 71 is not less than EMIN 82, software operation resumes with action 71. When action 79 is performed, the control processor 49 operates to stop charging of the battery by deactivating battery charging control 47 using enable line 52 and charging control level 53. After action 79 is performed, software operation resumes with action 71. The pre-programmed value EMIN 82, compared to the measured voltage of the energy storage capacitor 40, is chosen to be the minimum value sufficient to support a supply of battery charging current by battery charging control 47.
Operation of the software in control processor 49, once started, is intended to operate indefinitely. The software is only intended to stop operation when the regulated power provided by electronic voltage regulator 46 is at a value insufficient to operate control processor 49. Those skilled in the art will recognize that some energy may be saved by operating the control processor 49 periodically rather than continuously.
Referring to
As each heel strike 64 occurs there are corresponding currents flowing in the generators, shown in the plotted values of generator current 65. The occurrence of generator current 65 causes an increase in the plotted energy storage voltage 66. This exemplary form of generator current 65 shows current generated during both the heel compression mode of ambulation, as well as heel extension mode when the foot is lifted.
Those skilled in the art of electrical circuit operation will recognize the general form of the unloaded energy harvesting seen in energy storage voltage 66 as an exponential response. Those skilled in the art of electrical circuit operation will also recognize the decrease in the generator current 65 over time corresponding to the increase in energy storage voltage 66. As depicted in
It is a general characteristic of the rectifier assembly and capacitors 45 circuit that generator current 65 will increase as energy storage voltage 66 decreases for a constant level of heel strike 64 force input. If the average rate of energy recovery exceeds the electrical load of electronic voltage regulator 46, the energy storage voltage 66 will trend towards a stable average value, as further described in
Referring to
As the control processor 49 continues performing the control logic operations depicted in
As battery charging control 47 operation is stopped at point 99, consequently load current 68 decreases to continue operation with the control processor 49 as the only load. If energy harvesting operation continues at a sufficient rate, voltage 67 may increase. If at any time the energy harvesting operation is at a low level or stops, voltage 67 may decrease to a voltage value where the electronic voltage regulator 46 can no longer operate, and control processor 49 will stop. Under this condition, operation of the electronic voltage regulator 46 will only resume if the voltage 67 rises to a sufficient level, as determined by the circuit in
Those skilled in the art of electrical circuit operation will recognize that the operating characteristics are managed by the designer through choices of the electrical generation capacity, energy harvesting capacity, and energy storage capacity balanced against the energy consumption required by the prosthetic equipment loads.
It is to be appreciated and will be apparent to those skilled in the art that many variations in the implementation of the present invention are possible. An exemplary procedure for the determination of a specific implementation can start with the specification of the required output in terms of total energy, voltage, current, and dynamic responses. Applying a knowledge of the user's prosthetic application requirements in terms of forces and frequency of use can be used to determine the magnitude of harvestable energy. For the present invention the required component specifications can be determined by engineering calculations determining required capacities and power levels. The disposition and number of generators are variable according to the form of flexible prosthetic foot being used, and the desired level of energy harvesting. Current electronic component device technology can provide overall energy harvesting and conversion efficiency in the form of the present invention of approximately 50% or greater.
An exemplary variation of the generators includes those with integral gear train assemblies to increase generator speed. In concert with the mechanical link, drive gears, and generator selection a wide range of energy harvesting operating voltages and capacities are possible.
Having thus described in detail a preferred embodiment of the present invention APPARATUS FOR PROSTHETIC LEG VACUUM UNIT BATTERY RECHARGING, it is to be appreciated and will be apparent to those skilled in the art that many changes not exemplified in the detailed description of the invention could be made without altering the inventive concepts and principles embodied therein. It is also to be appreciated that numerous embodiments incorporating only part of the preferred embodiment are possible which do not alter, with respect to those parts, the inventive concepts and principles embodied therein.
The presented embodiments are therefore to be considered in all respects exemplary and/or illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and all alternate embodiments and changes to the embodiments shown herein which come within the meaning and range of equivalency of the appended claims are therefore to be embraced therein. It is also to be appreciated that prosthetic applications using a vacuum assisted socket mounting sleeve for below, at, or above knee applications can be served by the present invention.
