System and method for controlling power in machine having electric and/or hydraulic devices

Disclosed is a system for controlling power in a machine. The system includes a controller configured to determine a level of power to be provided or consumed by at least one of an electric device and a hydraulic device based on request signals, operation signals, and a control strategy for controlling at least one of electric power and hydraulic power for the machine, and provide control signals for controlling operation of the at least one device. The control strategy includes a subsystem control and a supervisory control. The subsystem control includes at least one of electric and hydraulic subsystem controls for controlling operation of at least one of an electric device and a hydraulic device. The subsystem control is configured to provide range signals indicative of at least one of a range of acceptable electric power levels and a range of acceptable hydraulic power levels, and the supervisory control is configured to determine the control signals.

TECHNICAL FIELD

The present disclosure relates to a system and method for controlling power in a machine having electric and/or hydraulic devices, and more particularly, to a system and method for controlling electric and/or hydraulic devices configured to provide and consume power.

BACKGROUND

Some conventional machines have a hydraulic power source for operating hydraulic actuators. For example, such a machine might typically include an internal combustion engine for driving one or more hydraulic pumps, which, in turn, supply power to one or more hydraulic actuators for performing work. One example of such a machine is a hydraulic excavator. A hydraulic excavator may typically include one or more hydraulic pumps, which provide hydraulic power in the form of pressurized fluid flow to one or more hydraulic motors and hydraulic cylinders for operation of a boom, stick, and digging implement. In such a machine, the hydraulic motors may be used to rotate a cab relative to a chassis on which the cab is mounted and drive grounding engaging wheels or tracks for movement of the machine. Hydraulic power provided to the hydraulic actuators may be used to raise and lower the boom and manipulate the stick and the digging implement in order to perform digging and/or loading operations.

To increase the efficiency and/or reduce undesirable emissions resulting from operation of the internal combustion engine, efforts have been made to recapture some of the energy typically lost during operation of such a machine. For example, energy may be recaptured in the form of stored electric and hydraulic energy for use by electric and hydraulic devices. Thus, it may be desirable to perform some working functions in a machine with both stored hydraulic energy and stored electric energy by use of both electric and hydraulic devices. However, in such a machine it may be difficult to control the supply of electric and hydraulic power to the electric and hydraulic devices in a manner that results in desirable performance and/or efficiency. Therefore, it may be desirable to provide a system and method for controlling power in a machine having both electric and hydraulic devices in a manner that results in the machine having the desired performance and/or efficiency.

A hybrid construction machine is disclosed U.S. Pat. No. 7,669,413 B2 to Komiyama et al. (“the '413 patent”). In particular, the '413 patent discloses a hybrid excavator including a hydraulic pump, a generator motor connected in parallel to an output shaft of an engine, and a rotation motor driven by a battery. The generator motor assists the engine by performing a motor function. Power consumption of each of the hydraulic pump and the rotation motor is detected, and the output of the hydraulic pump and the rotation motor is controlled such that the sum of the detected power consumption does not exceed a maximum supply power set as the sum of power that can be supplied to the hydraulic pump and the rotation motor.

Although the machine disclosed in the '413 patent includes both electric and hydraulic devices, the machine disclosed in the '413 patent may still fail to control the electric and hydraulic devices in the machine in a manner providing desirable machine performance and efficiency. Therefore, it may be desirable to provide a system and method for controlling power in a machine having both electric and hydraulic devices in a manner that results in the machine having the desired performance and efficiency.

SUMMARY

In one aspect, the present disclosure includes a system for controlling power in a machine. The system includes a controller configured to receive request signals indicative of requested operation of at least one of an electric device and a hydraulic device and operation signals from the at least one device, the operation signals being indicative of a status of the at least one device. The controller is also configured to determine a level of power to be provided or consumed by the at least one device based on the request signals, the operation signals, and a control strategy for controlling at least one of electric and hydraulic power for the machine, and provide control signals for controlling operation of the at least one device. The control strategy includes a subsystem control and a supervisory control. The subsystem control includes at least one of an electric subsystem control for controlling operation of an electric device and a hydraulic subsystem control for controlling operation of a hydraulic device. The subsystem control is configured to provide range signals for at least one of an electric device and a hydraulic device, the range signals being indicative of at least one of a range of acceptable electric power levels and a range of acceptable hydraulic power levels associated with operation of the at least one device. The supervisory control is configured to determine the control signals for controlling operation of the at least one device based on the operation signals, the range signals, and the request signals indicative of requested operation of the at least one device.

According to another aspect, the disclosure includes a method for controlling power in a machine comprising an electric device configured to provide electric power and consume electric power, and a hydraulic device configured to provide hydraulic power and consume hydraulic power. The method includes receiving request signals indicative of requested operation of the electric and hydraulic devices, and receiving operation signals from the electric and hydraulic devices, the operation signals being indicative of a status of the electric and hydraulic devices. The method further includes determining a level of power to be provided or consumed by the electric and hydraulic devices based on the request signals, the operation signals, and a control strategy for controlling electric and hydraulic power for the machine. The method further includes providing control signals for controlling operation of the electric and hydraulic devices, wherein the control strategy includes subsystem controls and a supervisory control. The subsystem controls include an electric subsystem control for controlling operation of the electric device and a hydraulic subsystem control for controlling operation of the hydraulic device. The subsystem controls are configured to provide range signals for the electric and hydraulic devices, the range signals being indicative of a range of acceptable electric and hydraulic power levels associated with operation of the electric and hydraulic devices. The supervisory control is configured to determine the control signals for controlling operation of the electric and hydraulic devices based on the operation signals, the range signals, and the request signals indicative of requested operation of the electric and hydraulic devices.

According to a further aspect, the disclosure includes a machine including a chassis, an operator interface for controlling operation of the machine, an electric device coupled to the chassis, a hydraulic device coupled to the chassis, and a controller. The controller is configured to receive request signals indicative of requested operation of the electric and hydraulic devices, and receive operation signals from the electric and hydraulic devices, the operation signals being indicative of a status of the electric and hydraulic devices. The controller is further configured to determine a level of power to be provided or consumed by the electric and hydraulic devices based on the request signals, the operation signals, and a control strategy for controlling electric and hydraulic power for the machine. The controller is further configured to provide control signals for controlling operation of the electric and hydraulic devices, wherein the control strategy includes subsystem controls and a supervisory control. The subsystem controls include an electric subsystem control for controlling operation of the electric device and a hydraulic subsystem control for controlling operation of the hydraulic device. The subsystem controls are configured to provide range signals for the electric and hydraulic devices, the range signals being indicative of a range of acceptable electric and hydraulic power levels associated with operation of the electric and hydraulic devices. The supervisory control is configured to determine the control signals for controlling operation of the electric and hydraulic devices based on the operation signals, the range signals, and the request signals indicative of requested operation of the electric and hydraulic devices.

DETAILED DESCRIPTION

FIG. 1shows an exemplary embodiment of a machine10for performing work. In particular, the exemplary machine10shown inFIG. 1is an excavator for performing operations such as digging and/or loading material. Although the exemplary systems and methods disclosed herein are described in relation to an excavator, the disclosed systems and methods have applications in other machines such as an automobile, truck, agricultural vehicle, work vehicle, wheel loader, dozer, loader, track-type tractor, grader, off-highway truck, or any other machines known to those skilled in the art.

As shown inFIG. 1, exemplary machine10includes a chassis12flanked by ground-engaging members14for moving machine10(e.g., via ground-engaging tracks or wheels). Machine10includes an operator cab16mounted to chassis12in a manner that permits rotation of cab16with respect to chassis12. A boom18is coupled to cab16in a manner that permits boom18to pivot with respect to cab16. At an end opposite cab16, a stick20is coupled to boom18in a manner that permits stick20to pivot with respect to boom18. At an end opposite boom18, an implement22(e.g., a digging implement or bucket) is coupled to stick20in a manner that permits implement22to pivot with respect to stick20. Although exemplary machine10shown inFIG. 1includes a digging implement, other tools may coupled to stick20when other types of work are desired to be performed.

In the exemplary embodiment shown, a pair of actuators24are coupled to cab16and boom18, such that extension and contraction of actuators24raises and lowers boom18, respectively, relative to cab16. An actuator26is coupled to boom18and stick20, such that extension and retraction of actuator26results in stick20pivoting inward and outward, respectively, with respect to boom18. Actuator28is coupled to stick20and digging implement22, such that extension and retraction of actuator28results in digging implement22pivoting between closed and open positions, respectively, with respect to stick20.

As explained in more detail with respect toFIG. 2, exemplary actuators24,26, and28are hydraulic devices, in particular, hydraulic cylinders powered by supplying and draining fluid from the cylinders on either side of a piston to cause reciprocating movement of the piston within the cylinder. One or more of actuators24,26, and28may be non-hydraulic actuators without departing from the concepts disclosed herein. In addition, the number of each of actuators24,26, and28coupled to boom18, stick20, and/or implement22, respectively, may be changed without departing from the concepts disclosed herein.

Referring toFIG. 2, exemplary machine10includes a power system30including electric and hydraulic devices operated respectively via electric and hydraulic power sources and controlled by a controller. In particular, exemplary power system30includes an internal combustion engine32. Engine32may be, for example, a compression-ignition engine, a spark-ignition engine, a gas turbine engine, a homogeneous-charge compression ignition engine, a two-stroke engine, a four-stroke, or any type of internal combustion engine known to those skilled in the art. Engine32may be configured to operate on any fuel or combination of fuels, such as, for example, diesel, bio-diesel, gasoline, ethanol, methanol, or any fuel known to those skilled in the art. Further, engine32may be supplemented by a hydrogen-powered engine, fuel-cell, solar cell, and/or any power source known to those skilled in the art.

In the exemplary embodiment shown, power system30includes an electric motor/generator34(e.g., an AC motor/generator) coupled to engine32, such that engine32drives motor/generator34, thereby generating electric power. Motor/generator34is electrically coupled to an inverter36(e.g., an AC-DC inverter), which, in turn, is electrically coupled to a bus38(e.g., a DC bus). The exemplary power system30further includes a converter40electrically coupled to bus38. Converter40may be a DC-DC bi-directional converter, which, in turn, is electrically coupled to an electric storage device42. Electric storage device42may include one or more batteries and/or ultra-capacitors configured to store electric energy supplied from motor/generator34and/or or any electrical energy generated by capturing energy associated with operation of machine10, such as energy captured from regenerative braking of moving parts of10machine, such as, for example, ground-engaging members14and/or rotation of cab16. Electric energy stored in electric storage device42may be used as a source of electric power as explained in more detail below.

Exemplary power system30further includes an inverter44(e.g., an AC-DC inverter) coupled to bus38. Inverter44is electrically coupled to an electric motor/generator46(e.g., an AC motor/generator). In the exemplary embodiment shown, motor/generator46is coupled to cab16such that operation of motor/generator46results in cab16rotating relative to chassis12. In addition, motor/generator46may be capable of slowing and stopping rotation of cab16in a regenerative manner that results in electric energy being generated that may be routed via inverter44, bus38, and converter40to electric storage device42for later supply to electric actuators such as motor/generators34and46. According to some embodiments, electric energy in electric storage device42may be routed via converter40, bus38, and inverter36to motor/generator34, which may then use the electric energy to supplement engine32and/or drive one or more of hydraulic pump/motors48aand48b, thus enabling electric power sources to assist engine32and/or hydraulic devices in machine10. According to some embodiments, electric energy generated by motor/generator34and/or motor/generator46may be routed between the two motor/generators34and46without necessarily being stored in electric storage device42, for example, by being routed from motor/generator46, via inverter44, bus38, and inverter36to motor/generator34, or from motor/generator34, via inverter36, bus38, and inverter44to motor/generator46.

In the exemplary embodiment shown inFIG. 2, engine32is coupled to two hydraulic pump/motors48aand48b, which may include fixed-displacement or variable-displacement pumps. Although the exemplary embodiment shown includes two pump/motors48aand48b, a single pump/motor or more than two pump/motors may be used. In the exemplary configuration shown, engine32supplies mechanical power to drive pump/motors48aand48b, which, in turn, provide hydraulic power to power system30by causing pressurized fluid to flow to and from hydraulic cylinders24,26, and28. In addition, according to some embodiments, one or more of pump/motors48aand48bmay supply power to engine32to assist with operation of engine32, for example, to drive motor/generator34, which may, in turn, supply electric power to electric devices of machine10.

In the exemplary embodiment shown inFIG. 2, pump/motors48aand48bare hydraulically coupled to control valves50, such that pump/motors48aand48bsupply pressurized fluid to control valves50, which, in turn, control fluid flow to and from hydraulic devices of machine10. For example, as shown inFIG. 2, control valves50are hydraulically coupled to hydraulic cylinders24,26, and28, and hydraulic pump/motor52, which, when supplied with pressurized fluid flow, drive ground-engaging members14. Although a single hydraulic motor52is shown, power system30may include one or more hydraulic motors52, for example, one for each of ground-engaging members14. Further, hydraulic pump/motor(s)52may be capable of slowing and stopping ground-engaging members14in a regenerative manner that results in hydraulic energy being generated that may be rerouted to provide hydraulic power to power system30, stored in a hydraulic storage device for later supply of hydraulic power to hydraulic actuators, and/or to provide hydraulic power to pump/motors48aand48b, which may supplement power of engine32, as explained in more detail below.

Exemplary power system30also includes an accumulator54hydraulically coupled to control valves50. Accumulator54is configured to store hydraulic energy captured during operation of power system30. For example, as explained above, hydraulic motor(s)52may be configured to slow movement of ground-engaging members14by operating as pumps such that ground-engaging members14drive the pumps, thereby slowing ground-engaging members14. The energy supplied to the hydraulic fluid by virtue of the pumping may be routed via control valves50for storage in accumulator54for later use, and/or to pump/motors48aand48b.

In the exemplary power system30, hydraulic cylinders24,26, and28are each hydraulically coupled to control valves50. As explained with respect toFIG. 1, hydraulic cylinders24,26, and28are respectively coupled to boom18, stick20, and implement22for manipulating boom18, stick,20, and implement22. Similar to hydraulic motor(s)52, hydraulic cylinders24,26, and28may be operated in a regenerative manner that results in hydraulic energy being generated, which may be rerouted to provide hydraulic power to power system30and/or stored in accumulator54. For example, if boom18is lowered from an elevated position, pressurized fluid is forced in a controlled manner from hydraulic cylinder24. This pressurized fluid may be routed via control valves50for storage in accumulator54, and/or to one or more of pump/motors48a,48b, and52for assisting operation of those hydraulic devices.

Exemplary power system30shown inFIG. 2includes a system55for controlling power system30. For example, power system30includes an operator interface56that may be contained in cab16. According to some embodiments, operator interface56may be located remote from machine10for remote control of machine10. Exemplary operator interface56includes a number of controls (e.g., levers, pedals, and/or buttons) for control of machine10and its functions. In the exemplary embodiment shown, operator interface56is coupled to control valves50, electrically and/or hydraulically, so that electric control signals and/or hydraulic control signals (e.g., via a hydraulic pilot circuit) may be sent from operator interface56to control valves50. Such electric and hydraulic control signals may be used to control operation of controls valves50for operation and control of the hydraulic devices of power system30. In addition, operator interface56is coupled electrically to a controller58configured to control operation of one or more electric and hydraulic devices of exemplary power system30, as explained in more detail below.

In addition, controller58may be coupled to a number of sensors associated with the devices of machine10in order to receive signals indicative of the operation of the devices. For example, machine10may include the following sensors: engine sensor32aassociated with engine32, motor/generator sensor34aassociated with motor/generator34, storage device sensor42aassociated with electric storage device42, motor/generator sensor46aassociated with motor/generator46, pump/motor sensors48cand48dassociated respectively with pump/motors48aand48b, hydraulic sensors24a,26a, and28aassociated respectively with hydraulic cylinders24,26, and28, accumulator sensor54aassociated with accumulator54, and pump/motor sensor52aassociated with pump/motor52. Each of the sensors identified above may include a single sensor or a number of sensors operating together to provide signals indicative of the operation of the associated device.

Engine sensor32amay include an engine speed sensor, a mass air-flow sensor, an emissions sensor, a manifold pressure sensor, a turbocharger boost pressure sensor, and/or other engine-related sensors. Motor/generator sensors34aand46amay include a speed sensor, a current sensor, a voltage sensor, and/or other motor/generator-related sensors. Storage device sensor42amay include a charge sensor, a current sensor, a voltage sensor, and/or other electric storage device-related sensors. Pump/motor sensors48c,48d, and52amay include a speed sensor, a flow rate sensor, a pressure sensor, and/or other hydraulic-related sensors. Accumulator sensor54amay include a pressure sensor and/or other hydraulic-related sensors.

Controller58may include one or more processors, microprocessors, central processing units, on-board computers, electronic control modules, and/or any other computing and control devices known to those skilled in the art. Controller58may be configured run one or more software programs or applications stored in a memory location, read from a computer-readable medium, and/or accessed from an external device operatively coupled to controller58by any suitable communications network.

Exemplary controller58is configured to control operation of power system30, including the engine and various electric and hydraulic devices of exemplary machine10. For example, controller58may be configured view each of the electric and hydraulic devices as both potential suppliers and consumers of electric and hydraulic power, and upon receipt of operator requests, control operation of the engine and electric and hydraulic devices in a coordinated manner to provide desired machine performance and efficiency.

For example, electric motor/generators34and46may operate by either consuming electric power or supplying electric power. They may consume electric power when operated to accelerate a device driven by motor/generators34and46. For example, motor/generator34may be driven to assist engine32with supplying power to hydraulic pump/motors48aand48b, and motor/generator46may be driven to rotate cab16. Motor/generator34may also supply electric power to power system30when operated to decelerate engine32(e.g., when engine32is coupled to a flywheel storage device (not shown)), using the generator portion of motor/generator34to generate electric power as driven by engine32. Motor/generator46may also operate to supply electric power to power system30in a similar manner when decelerating rotation of cab16. In addition, motor/generators34and46may supply electric power to each other and to energy storage device42when operating in a generator mode.

Energy storage device42may also operate as either a supplier or consumer of electric power. For example, energy storage device42may operate as a supplier of electric power by providing electric power to motor/generator34to assist output of engine32and/or to motor/generator46to rotate cab16. Electric storage device42may also act as a consumer of electric power when it stores electric power received from motor/generators34and46.

The hydraulic devices may also be viewed as both consumers and suppliers of hydraulic power. For example, pump/motors48a,48b, and52may operate by either consuming hydraulic power or supplying hydraulic power. They may consume hydraulic power when operated to increase the flow rate and/or pressure in the hydraulic system, for example, to operate hydraulic cylinders24,26, and28against a load. In addition, pump/motors48a,48b, and52may operate to consume hydraulic power to drive another of the pump/motors and/or to provide pressurized fluid to accumulator54. For example, one or more of pump/motors48aand48bmay operate as a pump to provide fluid to drive pump/motor52to drive ground engaging members14for moving machine10.

Pump/motors48a,48b, and/or52may also supply hydraulic power to power system30. For example, as motion of the machine10is slowed via pump/motor52, pump/motor52may convert the kinetic energy of machine10by pumping hydraulic fluid, thereby supplying hydraulic power to power system30, which may be used by pump/motors48aand48bto assist engine32with supplying power to electric motor/generator34, to assist with operation of hydraulic cylinders24,26, and28against a load, and/or to supply pressurized fluid to accumulator54for storage.

Similarly, hydraulic cylinders24,26, and28may operate to either consume or supply hydraulic power. For example, as boom18is lowered, hydraulic cylinder24may operate to supply hydraulic power in the form of pressurized fluid to the hydraulic system, which may be used to supply power to pump/motors48a,48b, and52, other hydraulic cylinders26and28, and/or accumulator54. Hydraulic cylinder24may also operate as a power consumer when acting against a load (e.g., to raise boom18) by drawing hydraulic power from one or more of pump/motors48a,48b, and52, accumulator54, and/or other hydraulic cylinders26and28.

Accumulator54may also operate as either a supplier or consumer of hydraulic power. For example, accumulator54may operate as a supplier of hydraulic power by providing pressurized fluid to pump/motors48aand48bto assist output of engine32, to hydraulic cylinders24,26, and28to act against a load, and/or to pump/motor52to drive ground engaging members14. Accumulator54may operate as a consumer of hydraulic power when it stores hydraulic power in the form of pressurized fluid received from pump/motors48a,48b, and52, and/or hydraulic cylinders24,26, and28.

Exemplary controller58is configured to receive request signals indicative of requested operation of the electric and hydraulic devices, for example, signals received from operator interface56, and control electric and hydraulic power in machine10according to a control strategy. For example, controller58may be configured to receive the request signals from interface56and operation signals from the electric and hydraulic devices upon receipt of the request signals. The operation signals are indicative of the status of the respective electric and hydraulic devices at the time of receipt of the request signals. For example, the operation signals may be signals received from the sensors associated with the respective electric and hydraulic devices and may include information about the power being supplied or consumed by the electric and hydraulic devices upon receipt of the request signals. The operation signals may also be indicative of the ability of the electric and hydraulic devices to either provide power or consume power upon receipt of the request signals by controller58. According to some embodiments, operation signals may also include signals associated with operation of engine32. Controller58may determine the level of power to be supplied or consumed by engine32and the electric and hydraulic devices based on the request signals, the operation signals, and the control strategy, and provide control signals for controlling operation of engine32and the electric and hydraulic devices of machine10.

FIG. 3is a schematic diagram of an exemplary control strategy60for operation of engine32and electric and hydraulic devices in exemplary machine10. As shown inFIG. 3, exemplary control strategy60includes subsystem controls62and a supervisory control64. Exemplary subsystem controls62include an engine subsystem control62afor controlling operation of engine32, an electric subsystem control62bfor controlling operation of the electric devices of the electric subsystem, and a hydraulic subsystem control62cfor controlling operation of the hydraulic devices of the hydraulic subsystem. Some embodiments may include additional subsystem controls for controlling operation of other devices.

Subsystem controls62are configured to provide supervisory control64with the request signals66indicative of the requested operation of the electric and hydraulic devices. According to some embodiments, supervisory control64may receive request signals66directly from a source other than subsystem controls62, such as, for example, interface56and/or engine32and the electric and hydraulic devices themselves.

Subsystem controls62are also configured to provide request and range signals for operation of the energy storage devices associated with the respective electric subsystem and the hydraulic subsystem based on the interrelationship of operation of the devices within the respective subsystem. For example, within the electric subsystem, electric subsystem control62bprovides request signals for controlling operation of electric storage device42based on the operation of the other devices within the electric subsystem. Similarly, within the hydraulic subsystem, hydraulic subsystem control62cprovides request signals for controlling operation of accumulator54based on the operation of the other devices within the hydraulic subsystem.

Subsystem controls62are also configured to provide range signals68indicative of a range of acceptable electric and hydraulic power levels associated with operation of the electric and hydraulic devices upon receipt of request signals66. Range signals68may also be based on how the device functions within a respective subsystem. For example, for the electric subsystem, range signals68for the respective electric devices may be based on the interrelationship of the operation of the electric devices within the electric subsystem, for example, as explained in more detail below with respect to electric storage device42. Similarly, for the hydraulic subsystem, range signals68for the respective hydraulic devices may be based on the interrelationship of the operation of the hydraulic devices within the hydraulic subsystem, for example, as explained in more detail below with respect to accumulator54.

Supervisory control64is configured to determine control signals70for controlling operation of engine32and the electric and hydraulic devices based on operation signals72(described previously herein), range signals68, and request signals66indicative of requested operation of the electric and hydraulic devices. In this exemplary manner, controller58evaluates operation of engine32and the electric and hydraulic devices, the requested operation of the devices, and controls operation of engine32and the devices in a coordinated manner to provide the desired machine performance and improve efficiency.

According to some embodiments, the range of acceptable electric power and hydraulic power levels is indicative of maximum and minimum power levels at which the electric and hydraulic devices are permitted to operate upon receipt of request signals66by controller58. For example, the maximum and minimum power levels may be based on the capacity of the respective device to supply power or consume power, or to supply or consume power based on predetermined design limits. For example, pump/motor48amay have a maximum pumping power output, and thus, the maximum power output level may be limited to the maximum pumping power output. As viewed from the perspective of engine32, this would represent a maximum power consumption limit. However, as viewed from the perspective of hydraulic cylinders24,26, and28, accumulator54, and pump/motor52, this would represent a maximum power supply limit. Alternatively, the maximum pumping power output of pump/motor48amight be limited based on a predetermined design limit, for example, to avoid excessive wear on pump/motor48aand/or other parts of machine10.

The minimum power levels of range signals68may relate to a predetermined lower limit of acceptable power output. For example, for pump/motors48aand48b, the lower limit may be associated with the minimum power output to provide hydraulic cylinders24,26, and28with sufficient hydraulic power to hold a load in implement22at a current height.

Engine32may also provide, via its associated sensors32a, operation signals72indicative of the status of engine32(e.g., the current power output and speed). Engine subsystem control62amay provide range signals68indicative of maximum and minimum power levels at which engine32is permitted to operate upon receipt of request signals66by controller58.

According to some embodiments, the ranges of acceptable electric, hydraulic, and engine power output levels provide limits for supervisory control64, so that supervisory control64does not provide control signals70for the electric devices, hydraulic devices, and engine32that fall outside the respective limits. As a result, although supervisory control64may determine a most efficient solution (i.e., based on power consumption considerations alone) for operating the power output levels of engine32and the electric and hydraulic devices, the ranges may prevent unintended and undesirable consequences of the most efficient solution.

For example, upon receipt of a request for deceleration of the rotation of cab16by controller58, motor/generator46may operate as a generator, thereby supplying electric power to machine10. If motor/generator46increases the level of deceleration of cab16, it would supply a larger amount of electric power. However, this might result in the rotation of cab16stopping more quickly than the request calls for, thereby resulting in undesirable control characteristics. If motor/generator46decreases the level of deceleration of cab16, it would supply a smaller amount of electric power. However, this might result in the rotation of cab16stopping more slowly than the request calls for, thereby also resulting in undesirable control characteristics.

When controller58receives a request signal66for decelerating cab16, electric subsystem control62bmay determine a range of acceptable power supply levels for motor/generator46during deceleration. As noted above, because it might not be desirable for operation of machine10to reduce or increase the level of deceleration of cab16, electric subsystem control62bmay determine a narrow range of acceptable power supply levels under these circumstances. Thus, electric subsystem control62bwould provide to supervisory control64request signal66indicative of the requested operation of motor/generator46and range signal68indicative of a narrow range of acceptable power supply levels for motor/generator46. Supervisory control64would thereafter control operation of motor/generator46by determining a level of power supply to be provided by motor/generator46based on request signals66, operation signals72of engine32and the various devices of machine10, and range signal68received from electric subsystem control62b. Thereafter, control signals70are provided to motor/generator46to control its operation. Control signals70may be sent from supervisory control64to electric subsystem control62b, which may thereafter control operation of motor/generator46. According to some embodiments, control signals70may be sent directly to motor/generator46without necessarily being relayed through electric subsystem control62b.

As another example, during acceleration of cab16, controller58receives request signal66for acceleration, and motor/generator46operates as a motor, thereby consuming electric power from machine10. If motor/generator46increases the level of acceleration of cab16, it would consume a larger amount of electric power. If motor/generator46decreases the level of acceleration of cab16, it would consume a smaller amount of electric power.

Electric subsystem control62bmay determine a range of acceptable power consumption levels for motor/generator46during acceleration of cab16. For example, it might not be desirable for operation of machine10to increase the acceleration of cab16beyond the requested level. However, due to power limits in machine10or other considerations, it may be desirable to reduce the level of acceleration below the requested level. Thus, electric subsystem control62bmay provide a range of acceptable power consumption levels from a maximum equal to the requested level to a minimum well below the requested level. Electric subsystem control62bwould provide to supervisory control64a request signal66indicative of the requested operation of motor/generator46and a range signal68indicative of the range of acceptable power supply levels. Thereafter, supervisory control64, using control signals72, controls operation of motor/generator46, for example, in the manner previously described, by determining a level of power for consumption by motor/generator46based on request signal66and range signal68received from electric subsystem control62a, and operation signals72of engine32and the various devices of machine10.

Electric subsystem control62bmay determine a range for operation of electric storage device42based on the interrelationship of the operation of the electric devices within the electric subsystem. For example, if no electric devices are operating within electric subsystem, electric subsystem control62bmay provide supervisory control64with a request signal indicating no requests for electric devices and a range signal68for each of the electric devices, which indicates the ability of the electric devices, including electric storage device42, to supply power to engine32and/or hydraulic subsystem via supplement of power to engine32for operation of one or more of pump/motors48aand48b.

However, if, for example, a request signal66is received for rotation of cab16(via motor/generator46), electric subsystem control62bsupplies supervisory control64with request signals66for each of the electric devices, including electric storage device42. In addition, electric subsystem control62bprovides range signals68for each of the electric devices. For example, request signal66for operation of motor/generator46for rotation of cab16may request 50 units of electric power. Electric subsystem control62bdetermines that motor/generator34being driven by engine32has the ability to provide 40 units of electric power to motor/generator46to rotate cab16, and electric storage device42has the ability to provide 40 units of electric power to motor/generator46to rotate cab16. Thus, motor/generator34and electric storage device42have a total of 30 units of excess capacity to meet the requested rotation of cab16. Electric subsystem control62bdetermines respective range signals66for motor/generator34and electric storage device42indicating a range of power outputs of 0-40 units of power for each of motor/generator34and electric storage device42, and a request signal66of 50 units for motor/generator46for rotation of cab16. Electric subsystem control62balso determines a range signal for motor/generator46as outlined previously herein. Also, electric subsystem control62bdetermines request signals66for each of motor/generator34and electric storage device42to provide the 50 units of power to motor/generator46. For example, electric subsystem control62bdetermines that the request signal66for motor/generator34will be 40 units of power, and the request signal for electric storage device42will be 10 units of power, thereby corresponding to the 50 units of electric power requested for operation of motor/generator46to rotate cab16. The request signals66and range signals68are supplied to supervisory control64.

In this example, supervisory control64uses the request and range signals66and68from electric subsystem control62b, as well as similar signals from engine subsystem control62aand hydraulic subsystem control62c, to determine control signals70for controlling operation of engine32and the electric and hydraulic devices of machine10. For example, if electric power is not needed for supplementing engine32or the hydraulic system, supervisory control64may provide control signals70to electric subsystem control62b, such that motor/generator34supplies, for example, 40 units of power to motor/generator46, and electric storage device42supplies 10 units of power to motor/generator46, thereby meeting the requested 50 units to rotate cab16.

However, if supervisory control64determines that the hydraulic subsystem would benefit from power supplied by the electric subsystem, for example, if the hydraulic subsystem is unable to supply enough hydraulic power to meet the requested operation demands of the hydraulic subsystem, for example, because of limited capability of engine32and/or an inability of accumulator54to offset the limited capability of engine32, supervisory control64may determine that the electric subsystem may supply power to supplement operation of engine32by, for example, 20 units of power, thereby increasing the capability of the hydraulic subsystem. Because the output of pump/motors48aand48bmay be limited due to instantaneous engine capability, supplementing operation of engine32with the electric subsystem may enable an increase in the hydraulic power pump/motors48aand48bmay supply. Thus, in order to meet the 20-unit power demand for supplementing engine32and the 50-unit power demand of the request to rotate cab16, 70 units of power may be supplied from the combined 80 units of available power from motor/generator34and electric storage device42, so that 50 units are supplied to rotate cab16, and 20 units are supplied to hydraulic subsystem via power supplied to engine32.

In a similar manner, hydraulic subsystem control62cmay determine a range for operation of accumulator54based on the interrelationship of the operation of the hydraulic devices within the hydraulic subsystem. For example, if no hydraulic devices are operating within hydraulic subsystem, hydraulic subsystem control62cmay provide supervisory control64with a request signal indicating no requests for hydraulic devices and a range signal68for each of the hydraulic devices, which indicates the ability of the hydraulic devices, including accumulator54, to supply power to engine32and/or electric subsystem via supplement of power to engine32for operation of motor/generator34of the electric subsystem.

However, if, for example, a request signal66is received for movement of machine10(via pump/motor52and ground engaging members14), hydraulic subsystem control62csupplies supervisory control64with request signals66for each of the hydraulic devices, including accumulator54. In addition, hydraulic subsystem control62cprovides range signals68for each of the hydraulic devices. For example, request signal66for operation of pump/motor52for movement of machine10may request 60 units of electric power. Hydraulic subsystem control62cdetermines that pump/motors48aand48bbeing driven by engine32have the ability to provide 50 units of hydraulic power to motor/generator46to move machine10, and accumulator54has the ability to provide 30 units of hydraulic power pump/motor52to move machine10. (According to some embodiments, hydraulic cylinders24,26, and/or28may be used to supply hydraulic power to pump/motor52, as described previously herein.) Thus, pump/motors48aand48band accumulator54have a total of 20 units of excess capacity to meet the requested movement of machine10. Hydraulic subsystem control62cdetermines respective range signals66for pump/motors48aand48band accumulator54indicating a range of power outputs of 0-50 units for pump/motors48aand48band 0-30 units of power for accumulator54, and a request signal66of 60 units for pump/motor52for movement of machine10. Hydraulic subsystem control62calso determines a range signal for pump/motor52as outlined previously herein. Also, hydraulic subsystem control62cdetermines request signals66for each of pump/motors48aand48band accumulator54to provide the 60 units of power to pump/motor52. For example, hydraulic subsystem control62cdetermines that the request signal66for pump/motors48aand48bwill be 50 total units of power, and the request signal66for accumulator54(and/or hydraulic actuators24,26, and/or28) will be 10 units of power, thereby corresponding to the 60 units of hydraulic power requested for operation of pump/motor52to move machine10. The request signals66and range signals68are supplied to supervisory control64.

In this example, supervisory control64uses the request and range signals66and68from hydraulic subsystem control62c, as well as similar signals from engine subsystem control62aand electric subsystem control62b, to determine control signals for controlling operation of engine32and the electric and hydraulic devices of machine10. For example, if hydraulic power is not needed for supplementing engine32or the electric subsystem, supervisory control64may provide control signals70to hydraulic subsystem control62c, such that pump/motors48aand48bsupply, for example, 50 units of power to pump/motor52, and accumulator54supplies 10 units of power to pump/motor52, thereby meeting the requested 60 units to move machine10.

However, if supervisory control64determines that the electric subsystem would benefit from power supplied by the hydraulic subsystem, for example, if the electric subsystem was unable by itself to supply enough electric power to meet the requested operation demands of the electric subsystem, supervisory control64may determine that the hydraulic subsystem may supply power to supplement operation of engine32by, for example, 20 units of power. Thus, in order to meet the 20-unit power demand for supplementing engine32and the 60-unit power demand of the request to move machine10, 80 units of power may be supplied from the combined 80 units of available power from pump/motors48aand48band accumulator54, so that 60 units are supplied to move machine10, and 20 units are supplied to electric subsystem via power supplied to engine32.

FIG. 4shows a flow diagram of an exemplary embodiment of a method for controlling power in exemplary machine10. As shown inFIG. 4, exemplary method begins at step100with receipt of request signals66indicative of requested operation of the electric and hydraulic devices by controller58from, for example, operator interface56. Upon receipt of request signals66, at step110controller58receives operation signals72from the various sensors associated with operation of engine32and the electric and hydraulic devices. Operation signals72are indicative of the status of engine32and the electric and hydraulic devices, for example, and may provide information about the current capabilities of engine32and the various devices, such as the current power output, the current level of energy storage, the current power consumption, and the current ability to supply or consume power.

Following receipt of request signals66and operation signals72, at step120controller58determines the level of power to be supplied or consumed by engine32and the various electric and hydraulic devices of machine10. In this exemplary method, this determination is made based on request signals66, operation signals72, and control strategy60for controlling electric and hydraulic power for machine10, for example, by controlling operation of engine32and the electric and hydraulic devices.

According to the exemplary embodiment described previously herein, control strategy60includes engine subsystem control62afor controlling engine32, electric subsystem control62bfor controlling the electric devices of machine10, and hydraulic subsystem control62cfor controlling the hydraulic devices of machine10. Exemplary control strategy60also includes supervisory control64, which provides at step130control signals70for controlling operation of engine32and the electric and hydraulic devices based on request signals66, operation signals72, and signals received from engine subsystem control62a, electric subsystem control62b, and hydraulic subsystem control62c. Subsystem controls62provide range signals68indicative of the range of acceptable power levels (power consumption or supply levels) associated with operation of engine32and the electric and hydraulic devices.

According to this exemplary method, the power in machine10may be controlled in a manner resulting in machine10having desired operation characteristics and improved efficiency. In particular, engine32and the electric and hydraulic devices may be operated in a coordinated manner, so that they consume and supply power to machine10in an efficient manner, while still maintaining desirable operation characteristics.

The exemplary systems and methods described above include a combination of electric and hydraulic devices and a combination of electric and hydraulic storage devices. It is contemplated that the systems and methods described herein may not include both electric and hydraulic devices, or may not include both electric and hydraulic storage devices. For example, the systems and methods may be used in machines having electric devices and electric storage devices, or a combination of electric devices, electric storage devices, and non-hydraulic devices (e.g., non-hydraulic storage devices, such as, for example, a non-hydraulic, mechanical storage device such as a flywheel). Alternatively, the systems and methods may be used in machines having hydraulic devices and hydraulic storage devices, or a combination of hydraulic devices, hydraulic storage devices, and non-electric devices (e.g., non-electric storage devices, such as, for example, a non-electric, mechanical storage device such as a flywheel).

INDUSTRIAL APPLICABILITY

Exemplary machine10may be used for performing work. In particular, exemplary machine10shown inFIG. 1is an excavator for performing operations such as digging and/or loading material. Although the exemplary systems and methods disclosed herein are described in relation to an excavator, the disclosed systems and methods have applications in other machines such as an automobile, truck, agricultural vehicle, work vehicle, wheel loader, dozer, loader, track-type tractor, grader, off-highway truck, or any other machines known to those skilled in the art.

Exemplary system55for controlling power in machine10may be used to control power in a machine having both electric and hydraulic devices that may act as either power suppliers or consumers. In particular, exemplary system55controls the power supply and consumption of the electric and hydraulic devices in a manner that improves the efficiency of a machine, while maintaining desirable control characteristics of the machine. The electric and hydraulic devices may include electric and hydraulic storage devices as well as electric and hydraulic actuators, such as, for example, electric motors, electric generators, electric motor/generators, hydraulic pumps, hydraulic motors, hydraulic pump/motors, and hydraulic cylinders.