Patent Publication Number: US-10323384-B2

Title: Active damping ride control system for attenuating oscillations in a hydraulic actuator of a machine

Description:
TECHNICAL FIELD 
     The present disclosure relates to a hydraulic actuator of a machine. More particularly, the present disclosure relates to a ride control system and a method for attenuating oscillations in a hydraulic actuator of a machine. 
     BACKGROUND 
     Machines such as, but not limited to, wheel loaders are used to transport materials from one location to another. In a typical configuration of such a machine, a pair of hydraulic actuators may be provided for raising or lowering the boom relative to the frame of the wheel loader. Further, a bucket may be supported at the free end of the boom for hauling the materials. In some cases for example, when such a machine travels on an uneven ground surface, the ride quality of the wheel loader may be poor. In such cases, the poor ride quality of the machine may manifest itself as vibrations in the hydraulic actuators of the machine. It is hereby envisioned that due to the vibrations induced in the hydraulic actuators during operation, a stability of the machine itself may be negatively impacted and hence, the operator&#39;s comfort may be degraded significantly. Moreover the performance and service life of the hydraulic actuators may also deteriorate over time and use during such conditions of poor ride quality. 
     Many traditional designs of ride control systems are known in the art for attenuating vibrations induced in the hydraulic actuators. Most traditional designs of such previously known ride control systems typically involve the use of accumulators that are disposed in communication with a head end and/or a rod end of each hydraulic actuator. However, these accumulator may be expensive to install and operate. 
     Hence, there exists a need for an improved ride control system that is simple, cost-effective, and use of which also overcomes the aforementioned shortcomings. 
     SUMMARY OF THE DISCLOSURE 
     In one aspect, the present disclosure discloses a ride control system for operatively attenuating oscillations in a hydraulic actuator of a machine. The hydraulic actuator has a chamber and a piston block disposed within the chamber so as to define a head end chamber and a rod end chamber with mutually opposing faces of the piston block and the chamber. The ride control system is provided with a tank, and a variable displacement pump that is disposed downstream of the tank. The variable displacement pump is fluidly coupled to the tank via a primary supply line. Further, the variable displacement pump is also provided with a secondary supply line fluidly coupled downstream thereof. 
     The ride control system also includes a valve arrangement that is independently coupled to the tank, the variable displacement pump, and each of the head and rod end chambers of the hydraulic actuator. The valve arrangement is configured to operably attenuate oscillations of the piston block in the hydraulic actuator based at least partially on a pressure of fluid in the head end chamber of the hydraulic actuator and a displacement of the piston block in the hydraulic actuator. 
     In an embodiment, the valve arrangement includes four independent metering valves (IMVs) that can be disposed in the circuit to fluidly couple the hydraulic actuator to the variable displacement pump and the tank. In this embodiment, a first drain line fluidly couples the primary supply line with the head end chamber of the hydraulic actuator. The first drain line has a first independent metering valve (IMV) disposed therein. The first IMV is configured to operatively allow fluid to return from the head end chamber to the tank. The ride control system also includes a first supply line that fluidly couples the secondary supply line with the head end chamber of the hydraulic actuator. The first supply line has a second IMV disposed therein. The second IMV is configured to operatively supply fluid from the pump to the head end chamber of the hydraulic actuator. 
     Although four single IMVs are disclosed herein, in alternative embodiments, it can be contemplated to embody the valve arrangement using a pair of programmable split spool valves or a single spool valve in place of the four IMVs with suitable modifications, if required, in the hardware configurations of the given spool valve/s. 
     Also, it has been hereby contemplated to provide a first pressure sensor for measuring a pressure of fluid in the head end chamber of the hydraulic actuator. A displacement sensor is also provided for measuring a displacement of the piston block disposed in the hydraulic actuator. Alternatively, it can also be contemplated to implement other devices including, but not limited to, a linkage angle sensor to measure the linkage position and/or the cylinder displacement of the hydraulic actuator. The ride control system also includes a controller that is disposed in communication with each of the first pressure sensor, the displacement sensor, the first IMV, and the second IMV. Once the active ride control system is activated, the initial pressure of fluid in the head end chamber is measured by the first pressure sensor and is registered in the controller. When the head end pressure decreases below the registered pressure and if the deviation in the head end pressure is within a predetermined frequency range, the controller is configured to close the first IMV and open the second IMV so as to supply pressurized fluid from the pump into the head end chamber of the hydraulic actuator. 
     In an additional aspect of this disclosure, the controller is further configured to maintain the closed and open states of respective ones of the first IMV and the second IMV until the deviation in the pressure of fluid in the head end chamber is zero and the oscillations of the piston block in the hydraulic actuator is attenuated. 
     Additionally, a second supply line is also provided to fluidly couple the secondary supply line with the rod end chamber of the hydraulic actuator. The second supply line has a third IMV disposed therein. The third IMV is configured to operatively supply fluid from the pump to the rod end chamber of the hydraulic actuator. The ride control system also includes a second drain line that is configured to fluidly couple the primary supply line with the rod end chamber of the hydraulic actuator. The second drain line has a fourth IMV disposed therein. The fourth IMV is configured to operatively allow fluid to return from the rod end chamber to the tank. 
     Additionally, the ride control system also includes a second pressure sensor configured to measure a pressure of fluid in the rod end chamber of the hydraulic actuator, the second pressure sensor being disposed in communication with the controller. In an additional aspect of this disclosure, when the displacement of the piston block within the hydraulic actuator, as measured by the displacement sensor, is indicative of a positive displacement corresponding to an expansion of the hydraulic actuator, and if the pressure of fluid in the head end chamber as measured by the first pressure sensor is less than a pressure of fluid in the rod end chamber as measured by the second pressure sensor, then the controller is configured to open the second IMV and the third IMV so as to route fluid from the rod end chamber to the head end chamber. 
     Additionally, in a further aspect of this disclosure, the controller is further configured to close the third IMV when the pressure of fluid in the head end chamber is equal to or greater than the pressure of fluid in the rod end chamber. Also, the controller is further configured to close the fourth IMV when the third IMV is opened so as to prevent a flow of fluid from the rod end chamber of the hydraulic actuator to the tank via the second drain line. 
     In another aspect, embodiments of this disclosure have also been directed to a machine employing the ride control system of the present disclosure. Further, embodiments of this disclosure have also been directed to a method for attenuating oscillations in a hydraulic actuator of a machine. 
     Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a machine showing a pair of hydraulic actuators for operatively facilitating movement of a work implement, according to an exemplary embodiment of the current disclosure; 
         FIG. 2  is a schematic view of a control system, according to an embodiment of the current disclosure; 
         FIG. 3  is a low-level circuit diagram of the control system, according to an embodiment of the current disclosure; 
         FIG. 4  illustrates an exemplary configuration of the low-level circuit diagram of the control system in accordance with an exemplary embodiment of the current disclosure; and 
         FIG. 5  is a flowchart of a method for attenuating oscillations in a hydraulic actuator, according to an embodiment of the current disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to specific aspects or features, examples of which are illustrated in the accompanying drawings. Wherever possible, corresponding or similar reference numbers will be used throughout the drawings to refer to the same or corresponding parts. 
       FIG. 1  illustrates a side view of a machine  100 , according to an exemplary embodiment of the present disclosure. In the illustrated embodiment, the machine  100  is embodied as a wheel loader. The machine  100  may be a fixed or a mobile machine that is configured to perform one or more than one type of operation associated with an industry such as mining, construction, farming, transportation, or any other industry known in the art. For example, in alternative embodiments, the machine  100  may include an excavator, a dozer, a harvester, a backhoe or other types of machines known in the art. 
     The machine  100  includes a frame  102 . The frame  102  rotatably supports a set of ground engaging members  104  each of which is embodied as a wheel in the illustrated embodiment of  FIG. 1 . The ground engaging members  104  are configured to rotate about their respective axes thereby propelling the machine  100  on a ground surface. Alternatively, it can be contemplated to embody the set of ground engaging members  104  in the form of tracks (not shown) such that the tracks are configured to propel the machine  100 . 
     The machine  100  further includes a work implement  106  configured to perform various tasks at a worksite. The work implement  106  may be configured to engage, penetrate, or cut the surface of the worksite and/or move the earth to accomplish a predetermined task. The worksite may include, for example, a mine site, a landfill, a quarry, a construction site, or any other type of worksite. Moving the earth may be associated with altering the geography at the worksite and may form a part of a main job function, for example, a grading operation, a scraping operation, a leveling operation, a bulk material removal operation, or any other type of geography altering operation at the worksite. 
     In the illustrated embodiment, the work implement  106  is a bucket that is pivotally mounted to the frame  102  with the help of a linkage  108  e.g., a boom as shown in  FIG. 1 . The work implement  106  may be disposed on the frame  102  at a front end of the machine  100 . In this embodiment, the work implement  106  may be configured to perform a scooping operation so as to dig material from a pile on the work site and thereafter hold the material therein for transportation of the held material from one location to another. Although a bucket is disclosed herein, it will be acknowledged that a type and configuration of the work implement  106  disclosed herein may vary from one application to another depending on specific requirements of an application. Therefore, it may be noted that the type of work implement  106  disclosed herein is non-limiting of this disclosure. Other types of work implements may be implemented in place of the bucket depending on specific requirements of an application. 
     The machine  100  further includes a hydraulic actuator  110  pivotally coupled to the frame  102 . One end  112  of the hydraulic actuator  110  may be coupled to the linkage  108  for lowering and raising the work implement  106  relative to the frame  102 . As shown in the illustrated embodiment of  FIG. 1 , the work implement  106  has a pre-defined range of angular motion denoted by AA′. 
     It may be noted that other pre-defined ranges of motion may be possible depending on a type of machine used, a type of work implement used on the machine, and a configuration of linkages present on the machine for coupling the work implement to the frame of the machine. It is hereby envisioned that when a position of the work implement  106  is fixed relative to the frame  102  at a given point in its range of angular motion and the machine  100  experiences vibrations, for example, when travelling on an uneven ground surface, a weight of the work implement  106  and/or a payload of the work implement  106  may manifest itself as vibrations in the hydraulic actuator  110  of the machine  100 . 
     The present disclosure relates to a ride control system  200  that is configured to attenuate oscillations in the hydraulic actuator  110  of the machine  100 . Referring to  FIG. 2 , a schematic of the ride control system  200  and the hydraulic actuator  110  is shown. The hydraulic actuator  110  has a chamber  202  and a piston block  204  disposed within the chamber  202  so as to define a head end chamber  202   a  and a rod end chamber  202   b  with respective ones of mutually opposing faces  206 ,  210  and  208 ,  212  of the piston block  204  and the chamber  202 . As shown in  FIG. 2 , the ride control system  200  is provided with a tank  214 , and a variable displacement pump  216  that is disposed downstream of the tank  214 . The variable displacement pump  216  is fluidly coupled to the tank  214  via a primary supply line  218 . Further, the variable displacement pump  216  is also provided with a secondary supply line  220  fluidly coupled downstream thereof. 
     The ride control system  200  includes a first drain line  222  that is configured to fluidly couple the primary supply line  218  with the head end chamber  202   a  of the hydraulic actuator  110 . The first drain line  222  has a first independent metering valve (IMV)  224  disposed therein. The first IMV  224  is configured to operatively allow fluid to return from the head end chamber  202   a  to the tank  214 . The ride control system  200  also includes a first supply line  226  that is configured to fluidly couple the secondary supply line  220  with the head end chamber  202   a  of the hydraulic actuator  110 . The first supply line  226  has a second IMV  228  disposed therein, the second IMV  228  being configured to operatively supply fluid from the pump  216  to the head end chamber  202   a  of the hydraulic actuator  110 . 
     Additionally, the ride control system  200  is further provided with a second supply line  230  that is configured to fluidly couple the secondary supply line  220  with the rod end chamber  202   b  of the hydraulic actuator  110 . The second supply line  230  has a third IMV  232  disposed therein. The third IMV  232  is configured to operatively supply fluid from the pump  216  to the rod end chamber  202   b  of the hydraulic actuator  110 . The ride control system  200  also includes a second drain line  234  that is configured to fluidly couple the primary supply line  218  with the rod end chamber  202   b  of the hydraulic actuator  110 . The second drain line  234  has a fourth IMV  236  disposed therein. The fourth IMV  236  is configured to operatively allow fluid to return from the rod end chamber  202   b  to the tank  214 . 
     The ride control system  200  further includes a first pressure sensor  238  configured to measure a pressure of fluid in the head end chamber  202   a  of the hydraulic actuator  110 , and a second pressure sensor  240  configured to measure a pressure of fluid in the rod end chamber  202   b  of the hydraulic actuator  110 . Additionally, the ride control system  200  also includes a displacement sensor  242  that is configured to measure a displacement of the piston block  204  disposed in the hydraulic actuator  110 . The ride control system  200  also includes a controller  244  that is disposed in communication with each of the first pressure sensor  238 , the displacement sensor  242 , the first IMV  224 , and the second IMV  228 . 
     Once the ride control system  200  is activated, the initial pressure of fluid in the head end chamber  202   a  is measured by the first pressure sensor  238  and is registered in the controller  244 . According to an embodiment of this disclosure, if the pressure of fluid in the head end chamber  202   a  as measured by the first pressure sensor  238  decreases to a value that is below the registered pressure and if the deviation in the head end pressure is within a predetermined frequency range, then the controller  244  is configured to close the first IMV  224  and open the second IMV  228  so as to supply pressurized fluid from the pump  216  into the head end chamber  202   a  of the hydraulic actuator  110 .  216  into the head end chamber  202   a  of the hydraulic actuator  110 . 
     In an example, if the initial pressure of fluid in the head end chamber is 1500 kPa and the pressure in the head end chamber  202   a  drops to 100 kPa in a duration of 5 seconds, then the controller  244  may not be configured to close the first IMV  224  and open the second IMV  228 . However, in another example in accordance with the foregoing embodiment, if the initial pressure of fluid in the head end chamber  202   a  is 1500 kPa and the pressure in the head end chamber  202   a  drops from 1500 kPa to 100 kPa in a duration of 0.5 second, then the controller  244  may close the first IMV  224  and open the second IMV  228 . The predetermined frequency range disclosed herein can be advantageously estimated and set to a value by the controller  244 , for use and implementation in closing the first IMV  224  and opening the second IMV  228  for attenuating oscillations in the hydraulic actuator  110 , based on a variety of factors including, but not limited to, the pressure in the head end chamber  202   a,  a displacement of the piston block  204  in the hydraulic actuator  110 , a position and/or angle of the linkage  108  with respect to the frame  102  and the like. 
     In accordance with another embodiment, if the pressure of fluid in the head end chamber  202   a  as measured by the first pressure sensor  238  increases to a value that is above the registered pressure and if the deviation in the head end pressure is not within the predetermined frequency range, then the controller  244  is configured to open the first IMV  224  and close the second IMV  228  so as to drain fluid from the head end chamber  202   a  of the hydraulic actuator  110  to the tank  214 . 
     Additionally, when the pressure in the head end chamber  202   a  drops to a value below the registered initial pressure, the controller  244  is also configured to maintain the closed and open states of respective ones of the first IMV  224  and the second IMV  228  until the oscillations in the pressure of fluid in the head end chamber  202   a  is attenuated. 
     In a further embodiment, when the displacement of the piston block  204  within the hydraulic actuator  110 , as measured by the displacement sensor  242 , is indicative of a positive displacement corresponding to an expansion of the hydraulic actuator  110 , and if the pressure of fluid in the head end chamber  202   a  as measured by the first pressure sensor  238  is less than a pressure of fluid in the rod end chamber  202   b  as measured by the second pressure sensor  240 , then the controller  244  is further configured to open the third IMV  232  so as to route fluid from the rod end chamber  202   b  to the head end chamber  202   a.  This way, fluid that is routed from the rod end chamber  202   b  to the head end chamber  202   a  increases a pressure of the head end chamber  202   a  so that a pressure difference between the head end chamber  202   a  and the rod end chamber  202   b  is minimized until it reaches a zero difference. 
     Thereafter, when the pressure of fluid in the head end chamber  202   a  becomes equal to or greater than the pressure of fluid in the rod end chamber  202   b,  the controller  244  is configured to close the third IMV  232 . Further, when the third IMV  232  is opened, it is hereby contemplated that the controller  244  is also configured to close the fourth IMV  236  so as to prevent a flow of fluid from the rod end chamber  202   b  of the hydraulic actuator  110  to the tank  214  via the second drain line  234 . This way, the flow from the pump to the head end chamber  202   a    216  can be supplemented by the supply of fluid from the rod end chamber  202   b  to the head end chamber  202   a  and hence avoid a possibility of voiding occurring in the head end chamber  202   a  of the hydraulic actuator  110 . This also helps to eliminate the possibility of cavitation from occurring in the head end chamber  202   a  and improves an overall service life of the hydraulic actuator  110 . Additionally, the supplemental flow from the rod end chamber  202   b  to the head end chamber  202   a  helps in facilitating a decay of the oscillations more rapidly as compared to supplying fluid from the pump  216  alone, due to which, vibrations or oscillations of the piston block  204  in the hydraulic actuator  110  can be attenuated faster. 
       FIG. 3  illustrates a low-level circuit diagram  300  of the ride control system  200  from  FIG. 2 , according to an embodiment of the current disclosure. It may be noted that the low-level circuit diagram  300  disclosed herein is non-limiting of this disclosure. Various other suitable hardware and software may, additionally or optionally, be implemented for use with the low-level circuit diagram  300  of the ride control system  200  shown in the illustrated embodiment of  FIG. 3 . 
     It should be noted that the controller  244  of the present disclosure may be a single microprocessor or multiple microprocessors that include components for performing functions that are consistent with the present disclosure. Numerous commercially available microprocessors can be configured to perform the functions of the controller  244  disclosed herein. It should be appreciated that the controller  244  could readily be embodied in a general purpose microprocessor capable of controlling numerous functions associated with the ride control system  200  of the machine  100 . The controller  244  may also include a processor, a memory, a secondary storage device, and any other components for running an application. Various circuits may be associated with the controller  244  such as a power supply circuitry, a solenoid driver circuitry, a signal conditioning circuitry for e.g., an analog-to-digital converter circuitry, and other types of circuitry. Various routines, algorithms, and/or programs can be programmed within the controller  244  for execution thereof. Moreover, it should be noted that the controller  244  disclosed herein may be a stand-alone controller  244  or may be configured to co-operate with existing controller  244 /s, for example, an electronic control module (ECM) (not shown) of the machine  100  to perform functions that are consistent with the present disclosure. 
     With reference to  FIG. 3 , the ride control system  200  may include a pre-processing module  302  that is configured to receive pressure and displacement signals from respective ones of the pressure and displacement sensors  238 - 242  disclosed earlier herein. The pre-processing module  302  may also be configured to convert the pressure and displacement signals into a suitable format for facilitating further computations by the controller  244  and for subsequently realizing functions consistent with the present disclosure. 
     The ride control system  200  also includes a disturbance rejection module  304  that is disposed in communication with the pre-processing module  302 . The disturbance rejection module  304  is also disposed in communication with a command module  306  that is coupled with four electronically operable solenoids  308 - 314  in which one solenoid is provided for controlling a corresponding one of the first, second, third, and fourth IMVs  224 ,  228 ,  232 , and  236  disclosed herein. The pre-processing module  302  may be configured to operatively determine, from output signals of the first and second pressure sensors  238 ,  240  and the displacement sensor  242 , if oscillations are occurring in the pressure at the head end chamber  202   a  of the hydraulic actuator  110 . If so, the disturbance rejection module  304  is configured to send appropriate signals to the command module  306  for modulating one or more command signals of the command module  306  before such command signals are output to one or more of the four solenoids  308 - 314  so that corresponding position/s of one or more of the four IMVs  224 ,  228 ,  232 , and  236  is realized for attenuating any pressure oscillations within the hydraulic actuator  110 . 
       FIG. 4  illustrates an exemplary configuration of the low-level circuit diagram  300  of the ride control system  200  in which the controller  244  is implemented, at least in part, with use of a non-linear proportional controller  402  that is associated with a band-pass filter  404 . However, it should be noted that in alternative embodiments of this disclosure, other types of controllers including, but not limited to, an integral controller, a proportional-integral (PI) controller, or a non-linear proportional-integral-differential (PID) controller may be used in place of the proportional controller  402  disclosed herein. 
     Further, as shown in the illustrated embodiments of  FIGS. 3 and 4 , the command module  306  includes a first set of modules  406  for determining a current state of corresponding ones of the four IMVs and a second set of modules  408  for scheduling the current command to each of the four solenoids  308 - 314  (refer to  FIG. 3 ). It should be noted that the first and second sets of modules  406  (e.g.,  406   1 - 406   4 ),  408  (e.g.,  408   1 - 408   4 ) disclosed herein may be implemented with the help of any device/s known to persons skilled in the art for forming the command module  306  of the present disclosure. Based on the inputs received at the controller  244 , the controller  244  selectively and independently outputs appropriate command signals to the each of the four solenoids  308 - 314  for attenuating pressure oscillations in the hydraulic actuator  110 . 
     INDUSTRIAL APPLICABILITY 
       FIG. 5  depicts a flowchart showing a method  500  for operatively attenuating oscillations in the hydraulic actuator  110 . At step  502 , the method  500  includes measuring a displacement of the piston block  204  disposed in the hydraulic actuator  110 . At step  504 , the method  500  includes registering the event comprising movement of the linkage  108  relative to the frame  102  at the controller  244 . A sub-routine of the method  500  comprises steps  506 - 516  explanation to which is made hereinafter. 
     At step  506 , the method  500  includes measuring the pressure of fluid in the head end chamber  202   a  of the hydraulic actuator  110 . At step  508 , the method  500  further includes processing, with the help of the pre-processing module  302 , the pressure signals into a suitable format for facilitating further computations by the controller  244 . Also, the pre-processing module  302  may be configured to operatively determine, from output signals of the first and second pressure sensors  238 ,  240  and the displacement sensor  242 , if oscillations are occurring in the pressure at the head end chamber  202   a  of the hydraulic actuator  110  at a certain pre-determined frequency. If so, then at steps  510 - 512 , the method  500  further includes issuing, by the disturbance rejection module  304 , appropriate signals to the command module  306  for modulating one or more command signals of the command module  306  before such command signals are output to one or more of the four solenoids  308 - 314  so that corresponding position/s of one or more of the four IMVs  224 ,  228 ,  232 , and  236  is realized for attenuating any pressure oscillations within the hydraulic actuator  110 . 
     Moreover, at step  514 , a further sub-routine of the method  500  may also include filtering, with the help of one or more digital filters (not shown), the command signals being issued from the command module  306 . Although one band-pass filter  404  is disclosed herein, it should be noted that other types of digital filters, including, but not limited to, a high-pass filter, a low-pass filter, or even other band-pass filters may be employed in addition to the band-pass filter  404  disclosed herein. The types of digital filter/s employed in the ride control system  200  may depend on various factors including, but not limited to, system specific hardware configuration associated with components of the ride control system  200 , and any signal conditioning requirements to be met in order for the ride control system  200  to perform functions consistent with the present disclosure. 
     Upon filtering the command signals with the help of the digital filter/s, at step  516 , the method  500  then includes sending the appropriate command signals to one or more of the four solenoids  308 - 314  (see  FIG. 3 ) such that corresponding positions of the four IMVs  224 ,  228 ,  232 , and  236  can be realized for accomplishing functions disclosed herein. 
     Embodiments of this disclosure have applicability for use and implementation in attenuating oscillations in hydraulic actuators of machines. With use of embodiments disclosed herein, manufacturers of machines can do away with use of accumulators and therefore, implement the present ride control system  200  in machines in a fairly inexpensive manner as compared to traditionally known designs of ride control systems. 
     Moreover, as embodiments of the present disclosure allow manufacturers to do away with use of accumulators, a reliability of hardware associated with the present ride control system  200  in operation is improved. Consequently, costs, time, and effort previously incurred with maintenance and replacement of accumulators from traditionally known designs of ride control systems can be advantageously mitigated with use of the present ride control system  200 . 
     Further, as embodiments of the present disclosure disclose the use of independent metering valves (IMVs), each of which are quick to operate in response to input commands from the controller  244 , an attenuation of oscillations in the hydraulic actuator  110  may be accomplished more quickly as compared with the use of traditionally known ride control systems that typically employ one or more accumulators therein. 
     While aspects of the present disclosure have been particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by the modification of the disclosed machines, systems and methods without departing from the spirit and scope of what is disclosed. Such embodiments should be understood to fall within the scope of the present disclosure as determined based upon the claims and any equivalents thereof.