Mobile machine with assistive torque electro-hydraulic powered actuator system

Abstract

A mobile machine comprising a plurality of elements to be driven relative to a body portion of the mobile machine, a plurality of hydraulic actuator units configured to actuate the plurality of elements, a tank, first and second four-quadrant pumps connected to the tank, an electric power source, an electric motor, a hydraulic system extending between the actuator units and the tank and comprising first and second pressure rails, each hydraulic actuator comprising first and second ports, a first valve between the first port and both the first and second pressure rails to meter flow between the first pressure rail, the second pressure rail, and the first port, and a second valve between the second actuator port and both the first and second pressure rails to meter flow between the first pressure rail, the second pressure rail, and the second actuator port.

Description

MOBILE MACHINE WITH ASSISTIVE TORQUE ELECTRO-HYDRAULIC POWERED ACTUATOR SYSTEMTECHNICAL FIELD

[0001] The present disclosed subject matter relates generally to the field of mobile machines, and more particularly to a mobile machine with an improved electro-hydraulic powered actuator system.BACKGROUND

[0002] Mobile machines are generally land vehicles with attached machinery or equipment that are self-propelled or mobile and that, in contrast to automobiles, provide functionality beyond conveying people from one point to another. Mobile machines are known to include, without limitation, excavators, skid steers, forklifts, tractors, earthmovers, farm machinery, dump trucks, garbage trucks, mobile cranes, and other mobile construction equipment. Lift arm mobile machines are generally self-propelled construction vehicles that have one or more lift arms that support and actuate attached work tools or attachments, such as for example excavators, skid steer loaders, forklifts, and tractors.BRIEF SUMMARY

[0003] With parenthetical reference to the corresponding parts, portions or surfaces of the disclosed embodiment, merely for purposes of illustration and not by way of limitation, an improved mobile machine (20, 220) is provided comprising a first element (22, 23, 24, 26, 28, 29, 30, 226, 229) configured to be driven relative to a body portion (21, 217) of the mobile machine by a first hydraulic actuator (102a-102i, 202a-202c), the first hydraulic actuator configured to actuate the first element to be driven relative to the body portion of the mobile machine within a first range of motion, the first hydraulic actuator comprising a first actuator port (109a-109d, 109g, 209a-209c) and a second actuator port (HOa-l lOd, 110g, 210a-210c), a tank (60, 260), a first four-quadrant pump (50, 250) connected to the tank, a second four-quadrant pump (55, 255) connected to the tank, an electric power source (40, 240), an electric motor (45, 245) connected to the electric power source and configured to be supplied with a current, the motor connected to at least one of the first four-quadrant pump and the second four-quadrant pump, a hydraulicsystem extending between the first hydraulic actuator and the tank, the hydraulic system comprising a first pressure rail (51, 251) and a second pressure rail (56, 256), the first pressure rail connected to the first four-quadrant pump and the second pressure rail connected to the second four-quadrant pump, a first valve (115a-l 15j, 215a-215c) between the first actuator port of the first hydraulic actuator and both the first pressure rail and second pressure rail and operatively configured to meter flow between the first pressure rail, the second pressure rail, and the first actuator port of the first hydraulic actuator, a second valve (120a-120d, 115e-l 15j, 220a-220c) between the second actuator port of the first hydraulic actuator and both the first pressure rail and second pressure rail and operatively configured to meter flow between the first pressure rail, the second pressure rail, and the second actuator port of the first hydraulic actuator, a second element (22, 23, 24, 26, 28, 29, 30, 226, 229) configured to be driven relative to the body portion of the mobile machine by a second hydraulic actuator (102a-102i, 202a-202c), the second hydraulic actuator configured to actuate the second element to be driven relative to the body portion of the mobile machine within a second range of motion, the second hydraulic actuator comprising a third actuator port (109a-109d, 109g, 209a-209c) and a fourth actuator port (HOa-l lOd, 110g, 210a- 210c), the hydraulic system extending between the second hydraulic actuator and the tank, a third valve (115a-l 15j, 215a-215c) between the third actuator port of the second hydraulic actuator and both the first pressure rail and second pressure rail and operatively configured to meter flow between the first pressure rail, the second pressure rail, and the third actuator port of the second hydraulic actuator, a fourth valve (120a-120d, 115e- 115j , 220a-220c) between the fourth actuator port of the second hydraulic actuator and both the first pressure rail and second pressure rail and operatively configured to meter flow between the first pressure rail, the second pressure rail, and the fourth actuator port of the second hydraulic actuator, wherein actuation of the first object to be driven relative to the body portion of the mobile machine within the first range of motion is operatively controllable and actuation of the second object to be driven relative to the body portion of the mobile machine within the second range of motion is operatively controllable.

[0004] The first hydraulic actuator may comprise a first housing (104a-104d, 104g, 204a- 204c) having the first actuator port and the second actuator port. The first hydraulic actuator may comprise a linear hydraulic actuator (102a-102c, 102g-102i, 202a-202c) or a rotary hydraulic actuator (102d-102f). The hydraulic actuator may comprise a linear hydraulic actuator (102a-102c, 102g-l 02i, 202a-202c), the housing may comprise a hydraulic cylinder (104a-104d, 104g, 204a-204c) having a first hydraulic chamber (105a-c, 105g, 205a-205c) and a second hydraulic chamber (106a-c, 106g, 206a-206c), the linear hydraulic actuator may comprise a hydraulic piston (107a-c, 107g, 207a-207c) between the first hydraulic chamber and the second hydraulic chamber and an actuating rod (108a-c, 108g, 208a-208c) connected to the piston and configured to translate along an axis (103a-103c, 203a, 203b) with movement of the piston relative to the housing, and one of the housing or the actuating rod may be connected to the mobile machine and the other of the housing or the actuating rod may be connected to the element to be driven. The hydraulic actuator may comprise a rotary hydraulic actuator (102d-102f), the rotary hydraulic actuator may comprises a hydraulic motor (102d-102f), the hydraulic motor may comprises a hydraulic rotary element (107g) between the first actuator port and the second actuator port of the first housing and an actuating shaft (108d) connected to the rotary element and configured to rotate about an axis (101 d, lOle, lOlf) with movement of the rotary element relative to the housing, and one of the housing or the actuating shaft may be connected to the mobile machine and the other of the housing or the actuating shaft may be connected to the element to be driven. The hydraulic motor may be selected from a group consisting of a vane-type hydraulic motor, a radial-piston type hydraulic motor, an axial-piston type hydraulic motor, and a gear-type hydraulic motor.

[0005] The range of motion may comprise rotational motion about a rotational axis (10 Id, lOle, 10 If) or translational motion along a translation axis. The mobile machine may comprise a battery (40) supplying the current to the electric motor. The motor may be connected to both the first four-quadrant pump and the second four-quadrant pump. The first four-quadrant pump may comprise a first bidirectional pump (50, 250) connected to the electric motor and the second four-quadrant pump may comprise a second bidirectional pump (55, 255) connected to a second electric motor. The first valve may comprise a first three-way valve assembly (115a-l 15d, 215a- 215c) and the second valve may comprise a separate second three-way valve assembly (120a- 120d, 220a-220c). The first valve and the second valve may be in a single four- way valve assembly (115e- 115j). The mobile machine may comprise an excavator (20) or a skid steer loader (220) and the element to be driven may comprise a bucket (29, 229) configured to be lifted and tilted relative to the body portion of the mobile machine. The tank may be open to atmosphere.

[0006] The mobile machine may comprise a controller (41, 241) that receives input signals and outputs command signals to the electric motor, the first valve, and the second valve to control actuation of the object to be driven relative to the body portion of the mobile machine. The mobile machine may comprise a first rail sensor (54, 254) configured to sense a pressure of the first pressure rail and to provide a pressure input signal to the controller, a second rail sensor (59, 259) configured to sense a pressure of the second pressure rail and to provide a pressure input signal to the controller, a first actuator sensor (11 la-11 Ij, 21 la-211c) configured to sense a pressure of the first actuator port and to provide a pressure input signal to the controller, a second actuator sensor (112a-l 12j, 212a-212c) configured to sense a pressure of the second actuator port and to provide a pressure input signal to the controller, a third actuator sensor (l l la-l l lj, 21 la-211c) configured to sense a pressure of the third actuator port and to provide a pressure input signal to the controller, and a fourth actuator sensor (112a- 112j , 212a-212c) configured to sense a pressure of the fourth actuator port and to provide a pressure input signal to the controller. The controller may receive input signals from the first rail sensor, the second rail sensor, the first actuator sensor, the second actuator sensor, the third actuator sensor, and the fourth actuator sensor and may output command signals to the electric motor, the first valve, and the second valve as a function of the input signals from the first rail sensor, the second rail sensor, the first actuator sensor, the second actuator sensor, the third actuator sensor, and the fourth actuator sensor. The mobile machine may comprise a regenerative power stage to the electric motor and the electric motor may be controlled by the controller to operate in a regeneration mode.

[0007] The mobile machine may comprise a third element (22, 23, 24, 26, 28, 29, 30, 226, 229) configured to be driven relative to the body portion of the mobile machine by a third hydraulic actuator (102a-102i, 202a-202c), the third hydraulic actuator configured to actuate the third element to be driven relative to the body portion of the mobile machine within a third range of motion, the third hydraulic actuator comprising a fifth actuator port (109a-109d, 109g, 209a- 209c) and a sixth actuator port (HOa-l lOd, 110g, 210a-210c), the hydraulic system extending between the third hydraulic actuator and the tank, a fifth valve (115a-l 15j, 215a-215c) between the fifth actuator port of the third hydraulic actuator and both the first pressure rail and second pressure rail and operatively configured to meter flow between the first pressure rail, the second pressure rail, and the fifth actuator port of the third hydraulic actuator, a sixth valve (120a-120d,115e- 115j , 220a-220c) between the sixth actuator port of the third hydraulic actuator and both the first pressure rail and second pressure rail and operatively configured to meter flow between the first pressure rail, the second pressure rail, and the sixth actuator port of the third hydraulic actuator, wherein actuation of the third object to be driven relative to the body portion of the mobile machine within the third range of motion is operatively controllable.

[0008] In another aspect, a mobile machine is provided comprising a plurality of elements (22, 23, 24, 26, 28, 29, 30, 226, 229) configured to be driven relative to a body portion (21, 217) of the mobile machine, a plurality of hydraulic actuator units (lOOa-lOOi, 200a-200c) configured to actuate the plurality of elements to be driven relative to the body portion of the mobile machine, a tank (60, 260), a first four-quadrant pump (50, 250) connected to the tank, a second four- quadrant pump (55, 255) connected to the tank, an electric power source (40, 240), an electric motor (45, 245) connected to the electric power source and configured to be supplied with a current, the motor connected to at least one of the first four-quadrant pump and the second four- quadrant pump, a hydraulic system extending between the plurality of actuator units and the tank, the hydraulic system comprising a first pressure rail (51 , 251) and a second pressure rail (56, 256), the first pressure rail connected to the first four-quadrant pump and the second pressure rail connected to the second four-quadrant pump, and each of the plurality of hydraulic actuators comprising a first actuator port (109a-109d, 109g, 209a-209c) and a second actuator port (110a- 1 lOd, 110g, 210a-210c), a first valve (115a-l 15j, 215a-215c) between the first actuator port and both the first pressure rail and second pressure rail and operatively configured to meter flow between the first pressure rail, the second pressure rail, and the first actuator port, and a second valve (120a-120d, 115e-l 15j, 220a-220c) between the second actuator port and both the first pressure rail and second pressure rail and operatively configured to meter flow between the first pressure rail, the second pressure rail, and the second actuator port.

[0009] The mobile machine may comprise a controller (41, 241) in communication with the motor and the first and the second valves of each of the actuator units and the first valve and the second valve of each of the actuator units may meter flow between the first actuator port and the second actuator port and the first rail and the second rail as a function of a control signal from the controller.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The accompanying drawings are incorporated herein as part of the specification. The drawings described herein illustrate embodiments of the presently disclosed subject matter and are illustrative of selected principles and teachings of the present disclosure. However, the drawings do not illustrate all possible implementations of the presently disclosed subject matter and are not intended to limit the scope of the present disclosure in any way.

[0011] FIG. 1 is a representative perspective view of a first embodiment of an improved mobile machine.

[0012] FIG. 2 is a schematic system diagram of the mobile machine electro-hydraulic actuator system shown in FIG. 2.

[0013] FIG. 3 is a schematic of the electro-hydraulic actuator system of an actuator unit shown in FIG. 2 in a first example operating state.

[0014] FIG. 4 is a schematic of the electro-hydraulic actuator system of the actuator unit shown in FIG. 3 in a second example operating state.

[0015] FIG. 5 is a schematic of the electro-hydraulic actuator system of two actuator units shown in FIG. 2 in a first example load state.

[0016] FIG. 6 is a schematic of the electro-hydraulic actuator system of the two actuator units shown in FIG. 5 in a second example load state.

[0017] FIG. 7 is a schematic of the electro-hydraulic actuator system of the two actuator units shown in FIG. 5 in a third example load state.

[0018] FIG. 8 is a schematic of the electro-hydraulic actuator system of the two actuator units shown in FIG. 5 in a fourth example load state.

[0019] FIG. 9 is a schematic of the electro-hydraulic actuator system of an alternative actuator unit shown in FIG. 2.

[0020] FIG. 10 is a schematic of the electro-hydraulic actuator system of a second alternative actuator unit shown in FIG. 2 in a first example operating state.

[0021] FIG. 11 is a schematic of the electro-hydraulic actuator system of the second alternative actuator unit shown in FIG. 10 in a second example operating state.

[0022] FIG. 12 is a representative perspective view of a second embodiment of an improved mobile machine.

[0023] FIG. 13 is a schematic system diagram of the mobile machine electro-hydraulic actuator system shown in FIG. 12.DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] At the outset, it should be clearly understood that like reference numerals are intended to identify the same structural elements, portions or surfaces consistently throughout the several drawing figures, as such elements, portions or surfaces may be further described or explained by the entire written specification, of which this detailed description is an integral part. Unless otherwise indicated, the drawings are intended to be read (e.g., crosshatching, arrangement of parts, proportion, degree, etc.) together with the specification, and are to be considered a portion of the entire written description. As used in the following description, the terms “horizontal,” “vertical,” “left,” “right,” “up” and “down,” as well as adjectival and adverbial derivatives thereof (e.g., “horizontally,” “rightwardly,” “upwardly,” etc.), simply refer to the orientation of the illustrated structure as the particular drawing figure faces the reader. Similarly, the terms “inwardly” and “outwardly” generally refer to the orientation of a surface relative to its axis of elongation, or axis of rotation, as appropriate.

[0025] It is to be understood that the specific assemblies and systems illustrated in the attached drawings and described in the following specification are simply exemplary embodiments. Hence, specific dimensions, directions, or other physical characteristics relating to the embodiments disclosed are not to be considered as limiting, unless expressly stated otherwise. Also, although they may not be, like elements in various embodiments described herein may be commonly referred to with like reference numerals within this section of the application.

[0026] It is to be appreciated that the present teaching is by way of example only, not by limitation. The concepts herein are not limited to use or application with a specific system or method. Thus, although the instrumentalities described herein are for the convenience of explanation, shown and described with respect to exemplary embodiments, it will be appreciated that the principles herein may be applied equally in other types of systems and methods.

[0027] Where they are used herein, the terms “first,” “second,” and so forth, do not necessarily denote any ordinal, sequential or priority relation, but are simply used to distinguish one element or set of elements more clearly from another element or set of elements, unless specified otherwise.

[0028] Referring to the drawings, an improved electro-hydraulic powered actuator system for a mobile machine is provided, of which a first embodiment is generally indicated at 15. As shown in FIG. 2, system 15 generally comprises battery 40, system controller 41, motor drive electronics 42 connected to battery 40 and system controller 41, motor 45 powered by drive electronics 42, four-quadrant pump 50 driven by motor 45, hydraulic pressure rail 51 connected to pump 50 via pump port 52, four-quadrant pump 55 driven by motor 45, hydraulic pressure rail 56 connected to pump 55 via pump port 57, tank 60 connected to pump 50 via pump port 53 and connected to pump 55 via pump port 58, pressure sensor 54 in pressure rail 51, pressure sensor 59 in pressure rail 56, and a plurality of actuation units 100a, 100b, 100c, lOOd, lOOe, lOOf, 100g, lOOh, lOOi and lOOj connected to pressure rails 51 and 56, all of which are supported on mobile machine 20.

[0029] FIG. 1 is a perspective view of mobile machine 20. As shown in FIG. 1, in this exemplary embodiment mobile machine 20 is an excavator and generally comprises carriage and traction system 21 comprising left traction 22 and right traction 23, upper structure or platform 24 rotationally supported on lower carriage 21 at slew connection 25 and comprising operator cab 31, boom 26 rotationally supported by platform 24 at swing connection 27, arm 28 pivotally connected to the distal end of boom 26, bucket 29 pivotally connected to the distal end of arm 28, and blade 30 supported by carriage 21.

[0030] While in this embodiment, mobile machine 20 is an excavator, it should be appreciated that other types of mobile machines or vehicles with attached machinery or equipment that are self-propelled or mobile and that provide functionality beyond transport may be alternatives, including without limitation forklifts, skid steers, tractors, earthmovers, farm machinery, dump trucks, garbage trucks, mobile cranes, backhoe loaders, wheeled loaders, scrapers, graders, compactors, and other mobile construction equipment.

[0031] As shown in FIGS. 1 and 2, each of actuation units lOOa-lOOj controls a separate motion or control axis of mobile machine 20 about or along which parts or tools of mobile machine 20 are movable. In this embodiment, mobile machine includes ten separate control axesor degrees of freedom. Linear actuation unit 100a provides linear motion on axis 103a and controls actuation of bucket 29 relative to arm 28 about axis 101a. Linear actuation unit 100b provides linear motion on axis 103b and controls actuation of boom 26 relative to swing connection 27 of platform 24 about axis 101b. Linear actuation unit 100c provides linear motion on axis 103c and controls actuation of arm 28 relative to boom 26 about axis 101c. Rotary actuation unit lOOd controls rotation of platform 24 relative to carriage 21 at slew connection 25 about slew axis lOld. Rotary actuation unit lOOe drives left track 22 relative to carriage 21 about drive axis lOle and rotary actuation unit lOOf drives right track 23 relative to carriage 21 about drive axis 10 If. Linear actuation unit 100g controls the height of blade 30 relative to carriage 21 and actuation unit lOOi controls the angle of blade 30 relative to carriage 21 about axis lOli. Linear actuation unit lOOh controls rotation of boom 26 at swing connection 27 relative to platform 24 about axis lOlh. Auxiliary actuation unit lOOj is an accessory manifold configured to control actuation of an auxiliary axis such as for example and without limitation a thumb (not shown) to bucket 29 or other accessory or auxiliary implements or tools.

[0032] Hydraulic pressure control rail lines 51 run from pump 50 to each of actuator units lOOa-lOOj, and hydraulic pressure control rail lines 56 run from pump 55 to each of actuator units lOOa-lOOj. Pressure sensor 54 is in control line 51 between pump 50 and actuator units 100a- lOOj and pressure sensor 59 is in control line 56 between pump 55 and actuator units lOOa-lOOj. Hydraulic tank line 61 runs between pump 50 and tank 60, and hydraulic tank line 62 runs between pump 55 and tank 60. In this embodiment, hydraulic reservoir or tank 60 compensates for volumetric differences in the system and thermal oil expansion and contraction within the system and may be either discharged or recharged, as appropriate, to accommodate differential fluid volumes. In this embodiment, tank 60 is an open-to-atmosphere tank.

[0033] In this embodiment, motor 45 is a brushless D.C. variable-speed servo-motor that is supplied with a current via battery 40 and drive electronics 42. Motor 45 has an inner rotor with permanent magnets and a fixed non-rotating stator with coil windings. When current is appropriately applied through the coils of the stator, a magnetic field is induced. The magnetic field interaction between the stator and rotor generates torque which may rotate the motor output shaft. When the supplied current is of one polarity, the motor will rotate in one direction. When the supplied current supplied is of the opposite polarity, the motor will rotate in the oppositedirection. Accordingly, the motor will selectively apply a torque on its output shaft in one direction about the motor axis at varying speeds and will apply a torque on its output shaft in the opposite direction about the motor axis at varying speeds. Other motors may be used as alternatives. For example, variable speed stepper motors, brush motors, and induction motors may be used as alternatives to motor 45. Other electric power sources may be used as alternatives to battery or battery pack 40. For example, a hydrogen fuel cell electric power source may be used as an alternative.

[0034] System controller 41 is connected to battery system 40 and receives power from battery system 40. System controller 41 communicates with drive electronics 42 to supply a current of the appropriate magnitude and polarity to motor 45. Based on a resolver angular position feedback, drive electronics 42 generate and commutate the stator fields to vary the speed and direction of motor 45. Controller 41 receives drive commands and feedback from sensors in system 15, such as sensors 54, 59, 11 la-11 Ij, and 112a-l 12j, and controls motor 45 and valves 115a-115j, 120a-120j and 127a-127j, accordingly. Thus, pressure transducers and position transducers in system 15 may be fed back to motor controller 41.

[0035] In this embodiment, power or battery system 40 includes a regenerative power circuit to take advantage of a regenerative mode described below in which pump 50 or pump 55 and motor 45 are controlled to operate as a generator in a power generation mode when external regenerative forces, such as gravity loads, on hydraulic actuators lOOa-lOOj exceed a threshold drive pressure differential of pumps 50 and 55 and drive torque of motor 45. For example, when the drive axes of excavator 20 need to absorb gravitational forces and impact forces, motor 45 may be configured to operate as an electric generator that converts torque generated from such forces on one or more of pumps 50 and 55 into electricity that is stored in battery storage 40. In the regenerative mode, electric motor 45 is configured to act as an electric generator and includes a regenerative power stage. Motor controller 41 may detect the armature current generated by motor 45 in this capacity and transfers such current of the appropriate magnitude and polarity of motor 45 into battery 40. Thus, system 15 includes regenerative energy functionality.

[0036] In this embodiment, pumps 50 and 55 are each 4-quadrant variable speed bidirectional or reciprocating internal two-port pumps that can each operate as a pump and also as a motor. With four possible quadrants of operation, each of pumps 50 and 55 has two quadrants, quadrants1 and 3 for example, in which it acts as a pump when the flow rate or pressure gain and the torque have the same directions (both positive or both negative), and two quadrants, quadrants 2 and 4 for example, in which the pump acts as a motor or generator when the flow rate or pressure gain and the torque have the opposite direction (one negative and one positive). The pumping elements are capable of rotating in either direction, thereby allowing hydraulic fluid to flow in either direction, and because the pump can rotate in either rotational direction it can function as a pump or as a motor. This allows for oil to be added into and out of the system as system controller 41 closes the control loop of position or pressure. The shaft of each of pumps 50 and 55 is connected to the output shaft of motor 45 and the direction of flow of each of pumps 50 and 55 depends on the displacement (positive or negative) of the respective pump and the speed and output of the respective pump is variable with variations in the speed of motor 45.

[0037] In this embodiment, each of pumps 50 and 55 comprises a radial piston type 4- quadrant hydraulic pump having a plurality of radially positioned pistons disposed in cylinders in a cylinder block that is connected to the output shaft of motor 45 and rotates relative to a cam. Hydraulic fluid from pump 50 is fed to each cylinder and piston via a control journal having ports connected to lines 51 and 61, respectively, to produce rotational movement of the output shaft of pump 50. Hydraulic fluid from pump 55 is fed to each cylinder and piston via a control journal having ports connected to lines 56 and 62, respectively, to produce rotational movement of the output shaft of pump 55. Other types of 4 quadrant hydraulic pumps may be used as alternatives, including without limitation other radial-piston type hydraulic pumps, axial-piston type hydraulic pumps, and gear-type hydraulic pumps in which hydraulic pressure is transformed into torque in either a pump or motor mode.

[0038] As shown in FIG. 2, each of actuator units 100a, 100b, and 100c share a common configuration. With reference to FIG. 3, actuation unit 100a generally includes hydraulic piston assembly 102a, three-way valve 115a, three-way valve 120a, pressure sensor I l la, pressure sensor 112a, and safety valves 127a, 128a and 129a.

[0039] In this embodiment, hydraulic piston assembly 102a includes piston 107a slidably disposed within cylindrical housing 104a such that piston 107a may be driven in both directions relative to housing 104a. Piston 107a is connected to actuating rod 108a. Piston 107a sealingly separates chamber 105a from chamber 106a. As shown, one side of valve 115a communicateswith chamber 105a via port 109a and fluid line 113a. The opposite side of valve 115a selectively communicates with pressure rail 51 via fluid line 116a and pressure rail 56 via fluid line 117a. One side of valve 120a communicates with chamber 106a via port 110a and fluid line 114a. The opposite side of valve 120a selectively communicates with pressure rail 51 via fluid line 121a and pressure rail 56 via fluid line 122a. Pump 50, pump 55 and piston actuation unit 100a form a hydrostatic transmission, so piston 107a will extend rod 108a when fluid is drawn into chamber 105a through fluid port 109a from line 113a and out from chamber 106a through fluid port 110a and into line 114a. Piston 107a will retract rod 108a when fluid is drawn into chamber 106a through fluid port 110a from line 114a and out from chamber 105a through fluid port 109a and into line 113a.

[0040] In this embodiment, valve 115a is three-way three-port three-position solenoid valve controlled by controller 41. Valve 115a is configured with a first port connected to chamber 105a via line 113a and port 109a, a second port connected to pressure rail 51 via line 116a, and a third port connected to pressure rail 56 via line 117a such that valve 115a may be controlled to meter fluid flow between chamber 105a and pressure rail 51 in a first position, to meter flow between chamber 105a and pressure rail 56 in a second position, or to block flow between chamber 105a and both pressure rail 51 and pressure rail 56 in a third position. Valve 115a is energized to the first or second position to open flow through the valve in either direction between chamber 105a and either pressure rail 51 or pressure rail 56 and thereby allow equalization of fluid pressure on each side of the valve between chamber 105a and either pressure rail 51 or pressure rail 56, respectively. When valve 115a is de-energized, the spring of the solenoid valve will bias it to the third blocked port position and closed, thereby blocking flow in either direction through the valve. Thus, in the event of a power failure, valve 115a will default to the closed third position.

[0041] In this embodiment, valve 120a is three-way three-port three-position solenoid valve controlled by controller 41. Valve 120a is configured with a first port connected to chamber 106a via line 114a and port 110a, a second port connected to pressure rail 51 via line 121a, and a third port connected to pressure rail 56 via line 122a such that valve 120a may be controlled to meter fluid flow between chamber 106a and pressure rail 51 in a first position, to meter flow between chamber 106a and pressure rail 56 in a second position, or to block flow between chamber 106a and both pressure rail 51 and pressure rail 56 in a third position. Valve 120a is energized to thefirst or second position to open flow through the valve in either direction between chamber 106a and either pressure rail 51 or pressure rail 56 and thereby allow equalization of fluid pressure on each side of the valve between chamber 106a and either pressure rail 51 or pressure rail 56, respectively. When valve 120a is de-energized, the spring of the solenoid valve will bias it to the third blocked port position and closed, thereby blocking flow in either direction through the valve. Thus, in the event of a power failure, valve 120a will default to the closed third position.

[0042] In this embodiment, pressure sensor 11 la is a pressure transducer in line 113abetween valve 115a and chamber 105a and is configured to sense pressure in chamber 105a and provides a pressure input signal to controller 41. Similarly, pressure sensor 112a is a pressure transducer in line 114a between valve 120a and chamber 106a and is configured to sense pressure in chamber 106a and provides a pressure input signal to controller 41.

[0043] In this embodiment, actuator unit 100a includes hydraulic brake valve 127a having connected check valves 128a and 129a between pressure rails 51 and 56 and lines 113a and 114a, respectively, with check valves 128a and 129a between chambers 105a and 106a and valves 115a and 120a, respectively. In particular, valves 127a, 128a and 129a are operatively configured to hold piston 107a in a braked position relative to cylinder 104a. In this embodiment valve 127a is an active valve that employs an external actuation force to stay open, rather than a passive valve in which the operational state of open or closed is determined by the fluid the valve controls (e.g. : a check valve). In this embodiment valve 127a is two-way two-port solenoid valve. When energized, valve 127a is held open, thereby allowing equalization of fluid pressure on each side of the valve and flow through the valve in either direction. When valve 127a is de-energized, the spring of the solenoid valve will bias it to blocked port and closed, thereby blocking flow in either direction through the valve. Thus, in the event of a power failure, valve 127a will close and oneway check valves 128a and 129a will block flow out of and maintain pressure in chambers 105a and 106a to brake piston 107a and bucket 29.

[0044] As shown with reference to FIG. 3, rod 108a of actuation unit 100a may be operated to extend in a direction 17a when pressure on the chamber 105a side face of piston 107a is greater than pressure on the opposite chamber 106a side face of piston 107a, and fluid enters chamber 105a in through port 109a from line 113a and exits chamber 106a out through port 110a into line 114a. Based on relative pressure readings of sensors 54, 59, 1 I la and 112a, valve 115a may beoperated to connect line 1 13a and chamber 105a to either rail 51 or 56 depending on which is at a greater pressure (the high pressure rail) and valve 120a may be operated to connect line 114a and chamber 106a to the other rail 51 or 56 that is at a lower pressure (the low pressure rail). As shown with reference to FIG. 4, rod 108a of actuation unit 100a may be operated to retract in a direction 18a when pressure on the chamber 105a side face of piston 107a is less than pressure on the opposite chamber 106a side face of piston 107a, and fluid exits chamber 105a out through port 109a into line 113a and enters chamber 106a in through port 110a from line 114a. Based on relative pressure readings of sensors 54, 59, 11 la and 112a, valve 120a may be operated to connect line 114a and chamber 106a to either rail 51 or 56 depending on which is at a greater pressure (the high pressure rail) and valve 115a may be operated to connect line 113a and chamber 105a to the other rail 51 or 56 that is at a lower pressure (the low pressure rail). Thus, to provide a desired pressure differential on the opposite faces of piston 107a, valves 115a and 120a may be operated to connect to a desired pressure differential between rails 51 and 56.

[0045] In an example embodiment shown in FIG. 3, actuator rod 108a is operated to extend in a direction 17a opposite the force of a load 16 by operating motor 45 to drive pump 55 to provide high pressure in rail 56, operating valve 115a to connect port 109a of chamber 105a to now high pressure rail 56, and operating valve 120a to connect port 110a of chamber 106a to now low pressure rail 51. Accordingly, when valve 115a operatively connects actuator port 109a to pressure rail 56 to drive hydraulic actuator 102a opposite to an external force, valve 120a is operated to connect actuator port 110a to pressure rail 51 when pressure at actuator port 110a is higher relative to pressure rail 51 to thereby operate pump 50 as a motor in a regeneration mode.

[0046] In an example embodiment shown in FIG. 4, actuator rod 108a of actuation unit 100a is operated to retract in the same direction 18a as the force of load 16 by operating valve 120a to connect port 110a of chamber 106a to now high pressure rail 56, and operating valve 115a to connect port 109a of chamber 105a to now low pressure rail 51. Accordingly, valve 115a is operated to connect actuator port 109a to pressure rail 51 when pressure at actuator port 109a is higher relative to pressure rail 51 to thereby operate pump 50 as a motor in a regeneration mode. An example of load 16 may be the effects of gravity on bucket 29, which generates a retracting force 18a on rod 108a and piston 107a, which in turn is used to produce regenerative pressure onpump 50 when brake 127a is not activated and a regenerative torque on the shaft of motor 45 connected to pump 50.

[0047] As shown in FIG. 2, each of actuator units 100b and 100c are configured to operate in tandem with actuator unit 100a and generally have the same configuration and functionality as actuator unit 100a. Thus, actuator units lOOb-lOOc generally include hydraulic piston assemblies 102b and 102c, three-way three-port three-position solenoid valves 115b and 115c controlled by controller 41, three-way three-port three-position solenoid valves 120b and 120c controlled by controller 41, pressure sensors 111b and 111c, pressure sensors 112b and 112c, and safety valves 127b and 127c, 128b and 128c and 129b and 129c, respectively. Hydraulic piston assemblies 102b and 102c generally include pistons 107b and 107c, cylindrical housings 104b and 104c, actuating rods 108b and 108c, chambers 105b and 105c, chambers 106b and 106c, ports 109b and 109c, and ports 110b and 110c, respectively. One side of valves 115b and 115c communicate with chambers 105b and 105c via ports 109b and 109c and fluid lines 113b and 113c, the opposite side of valves 115b and 115c selectively communicate with pressure rail 51 via fluid lines 116b and 116c and pressure rail 56 via fluid lines 117b and 117c, one side of valves 120b and 120c communicate with chambers 106b and 106c via ports 110b and 110c and fluid lines 121b and 121c, the opposite side of valves 120b and 120c selectively communicate with pressure rail 51 via fluid lines 121b and 121c and pressure rail 56 via fluid lines 122b and 122c, and pump 50, pump 55 and piston actuation units lOOb-lOOc form a hydrostatic transmission, respectively.

[0048] Representative examples of how two or more actuator units may be operated in tandem are shown in FIGS. 5-8, with reference in these embodiments to the features of actuator units 100a and 100b as an example only. However, different numbers of actuator units, such as three or more, and different combinations and types of actuator units, may be used in system 15 as alternatives. As indicated, based on relative pressure readings of sensors 54, 59, I l la, 112a, 111b and 112a, the load conditions, and the operating commands, valve 115a may be operated to connect line 113a and chamber 105a to either rail 51 or 56, valve 120a may be operated to connect line 114a and chamber 106a to either rail 51 or 56, valve 115b may be operated to connect line 113b and chamber 105b to either rail 51 or 56, and valve 120b may be operated to connect line 114b and chamber 106b to either rail 51 or 56.

[0049] As shown with reference to FIG. 5 and by way of an example, under certain load conditions, system 15 may be configured to operate pump 55 as a hydraulic drive pump and to operate pump 50 as a regenerative motor. In this example embodiment, rail 56 is operated as the high pressure rail driven by pump 55 and rail 51 is operated as the low pressure rail. By operating valve 115a to connect port 109a of chamber 105a to low pressure rail 51, operating valve 120a to connect port 110a of chamber 106a to low pressure rail 51, operating valve 115b to connect port 109b of chamber 105b to high pressure rail 56, and operating valve 120b to connect port 110b of chamber 106b to low pressure rail 51, actuator 102a may be driven to retract rod 108a with the force of load 16a and actuator 102b may be driven to extend rod 108b against the force of load 16b. Accordingly, valve 115b may operatively connect actuator port 109b to pressure rail 56 to drive hydraulic actuator 102b opposite to an external force, and valve 120b may be operated to connect actuator port 110b to pressure rail 51 when pressure at actuator port 110b is higher relative to pressure rail 51 to thereby operate pump 50 as a motor in a regeneration mode. And valve 115a may operatively connect actuator port 109a to low pressure rail 51 as an external force drives hydraulic actuator 102a in the same direction as the external force when pressure at actuator port 109a is higher relative to pressure rail 51 to thereby operate pump 50 as a motor in a regeneration mode, and valve 120a may be operated to also connect actuator port 110a to pressure rail 51.

[0050] As shown with reference to FIG. 6 and by way of an example, under certain load conditions, system 15 may be alternatively configured to operate pump 50 as a hydraulic drive pump and to operate pump 55 as a regenerative motor. In this example embodiment, rail 51 is operated as the high pressure rail and rail 56 is operated as the low pressure rail. By operating valve 115a to connect port 109a of chamber 105a to low pressure rail 56, operating valve 120a to connect port 110a of chamber 106a to low pressure rail 56, operating valve 115b to connect port 109b of chamber 105b to high pressure rail 51, and operating valve 120b to connect port 110b of chamber 106b to low pressure rail 56, actuator 102a may be again driven to retract rod 108a with the force of load 16a and actuator 102b may be driven to extend rod 108b against the force of load 16b. Accordingly, valve 115b may operatively connect actuator port 109b to pressure rail 51 to drive hydraulic actuator 102b opposite to an external force, and valve 120b may be operated to connect actuator port 110b to pressure rail 56 when pressure at actuator port 110b is higher relative to pressure rail 56 to thereby operate pump 55 as a motor in a regeneration mode. And valve 115amay operatively connect actuator port 109a to low pressure rail 56 as an external force drives hydraulic actuator 102a in the same direction as the external force when pressure at actuator port 109a is higher relative to pressure rail 56 to thereby operate pump 55 as a motor in a regeneration mode, and valve 120a may be operated to also connect actuator port 110a to pressure rail 56.

[0051] As shown with reference to FIG. 7 and by way of an example, under certain load conditions, system 15 may be configured to operate pump 55 as a hydraulic drive pump and to also operate pump 50 as a hydraulic drive pump. In this example embodiment, rail 56 is operated as a high pressure rail and rail 51 is also operated as a high pressure rail. By operating valve 115a to connect port 109a of chamber 105a to pressure rail 56, operating valve 120a to connect port 110a of chamber 106a to pressure rail 56, operating valve 115b to connect port 109b of chamber 105b to pressure rail 51, and operating valve 120b to connect port 110b of chamber 106b to pressure rail 51, actuator 102a may be driven to extend rod 108a against the force of load 16a and actuator 102b may be driven to also extend rod 108b against the force of load 16b. Accordingly, valve 115b may operatively connect actuator port 109b to pressure rail 51 to drive hydraulic actuator 102b opposite to an external force, and valve 120b may be operated to connect actuator port 110b to pressure rail 51 given the difference in surface area on each side of piston 107b, or optionally valve 120b could be operated to connect actuator port 110b to pressure rail 56 if pressure at actuator port 110b is higher relative to pressure rail 56. And valve 115a may operatively connect actuator port 109a to pressure rail 56 to drive hydraulic actuator 102a opposite to an external force, and valve 120a may be operated to connect actuator port 110a to pressure rail 56 given the difference in surface area on each side of piston 107a, or optionally valve 120a could be operated to connect actuator port 110a to pressure rail 51 if pressure at actuator port 110a is higher relative to pressure rail 51.

[0052] As shown with reference to FIG. 8 and by way of an example, under certain load conditions, system 15 may be configured to operate pump 55 as a regenerative motor and to also operate pump 50 as a regenerative motor. In this example embodiment, rail 56 is operated as a low pressure rail and rail 51 is also operated as a low pressure rail. By operating valve 115a to connect port 109a of chamber 105a to pressure rail 56, operating valve 120a to connect port 110a of chamber 106a to pressure rail 56, operating valve 115b to connect port 109b of chamber 105b to pressure rail 51, and operating valve 120b to connect port 110b of chamber 106b to pressurerail 51, actuator 102a may be driven to retract rod 108a with the force of load 16a and actuator 102b may be driven to retract rod 108b with the force of load 16b. Accordingly, valve 115b may operatively connect actuator port 109b to pressure rail 51 as an external force drives hydraulic actuator 102b in the same direction as the external force to thereby operate pump 50 as a motor in a regeneration mode, and valve 120b may be operated to connect actuator port 110b to pressure rail 51 given the difference in surface area on each side of piston 107b, or optionally valve 120b could be operated to connect actuator port 110b to pressure rail 56 if pressure at actuator port 110b is higher relative to pressure rail 56. And valve 115a may operatively connect actuator port 109a to pressure rail 56 as an external force drives hydraulic actuator 102a in the same direction as the external force to thereby operate pump 55 as a motor in a regeneration mode, and valve 120a may be operated to connect actuator port 110a to pressure rail 56 given the difference in surface area on each side of piston 107b, or optionally valve 120a could be operated to connect actuator port 110a to pressure rail 51 if pressure at actuator port 110a is higher relative to pressure rail 51.

[0053] Different numbers of actuator units, different combinations and types of actuator units, and different loading conditions may be employed in the system so that, based on relative pressure readings of the system sensors and the system operating commands, the control valves may be operated to connect each of the actuator ports of the actuator units to either pressure rail and four- quadrant pump depending on pressure differentials to thereby take advantage of any regenerative energy in the system. Thus, in this example embodiment power source 40 includes a regenerative power circuit to take advantage of a regenerative mode in which pump 50 and / or pump 55 and motor 45 are controlled to operate as a generator in a power generation mode when external regenerative forces, such as gravity loads, on hydraulic assemblies lOOa-lOOj exceed a threshold drive pressure differential of pump 50 and / or pump 55 and drive torque of motor 45.

[0054] As shown in FIG. 2, each of actuator units 100g, lOOh, and lOOi share a common configuration. With reference to FIG. 9, actuation unit 100g generally includes hydraulic piston assembly 102g, single unit four- way valve 115g, pressure sensor I l lg, pressure sensor 112g, and safety valves 127a, 128a and 129a. Hydraulic piston assembly 102g, as well as hydraulic piston assemblies 102h and 102i, generally have the same configuration and functionality as hydraulic piston assembly 102a, and includes piston 107g, in cylindrical housing 104g, actuating rod 108g,chamber 105g, chamber 106g, port 109g, and port 110g, respectively. Pressure sensors I l lg and 112g, as well as pressure sensors 11 lb and l l lj and 112h and 112j, generally have the same configuration and functionality as pressure sensors 11 la and 112a, respectively.

[0055] Actuation unit 100g, as well as actuation units lOOh-lOOj, differ from actuation unit 100a in that valves 115a and 120a have been combined as single, unitary four-way valve assembly 115g. In this embodiment, valve 115g is a four-way four-port three-position solenoid valve controlled by controller 41. Valve 115g is configured with a first port connected to chamber 105g via line 113g and port 109g, a second port connected to chamber 106g via line 114g and port 110g, a third port connected to pressure rail 51 via line 116g, and a fourth port connected to pressure rail 56 via line 117g. Valve 115g may be controlled to meter fluid flow between chamber 105g and pressure rail 51 and between chamber 106g and pressure rail 56 in a first position, to meter flow between chamber 105g and pressure rail 56 and between chamber 106g and pressure rail 51 in a second position, or to block flow between both chambers 105g and 106g and pressure rails 51 and 56 in a third position. Valve 115g is energized to the first or second position to open flow through the valve in either direction between chambers 105g and 106g and either pressure rail 51 or pressure rail 56 and thereby allow equalization of fluid pressure on each side of the valve. When valve 115g is de-energized, the spring of the solenoid valve will bias it to the third blocked port position and closed, thereby blocking flow in either direction through the valve. Thus, in the event of a power failure, valve 115g will default to the closed third position.

[0056] In this embodiment, actuation units lOOg-lOOj are used to control the motion axes of excavator 20 that are not operated as frequently as motion axis 101a, 101b, 101c and lOld, for example. In this embodiment, actuation units lOOg-lOOj are also not utilized to provide regenerative power to system 15, thereby reducing complexity in the control of system 15 by controller 41.

[0057] As shown in FIG. 2, and with further reference to FIGS. 10 and 11, actuation unit lOOd generally includes hydraulic assembly 102d, three-way valve 115d, three-way valve 120d, pressure sensor 11 Id, pressure sensor 112d, and safety valves 127d, 128d and 129d. Valve 115d generally has the same configuration and functionality as valve 115a, valve 120d generally has the same configuration and functionality as valve 120a, and pressure sensors 11 Id and 112dgenerally have the same configuration and functionality as pressure sensors I l la and 112a, respectively.

[0058] Actuation unit lOOd differs from actuation unit 100a in that hydraulic assembly 102d is a rotary hydraulic actuator that imparts a rotary output about axis lOld rather than a linear piston hydraulic actuator that imparts a linear output. In this embodiment, hydraulic motor 102d is a vane-type hydraulic motor having centrically supported rotor 107d in housing 104d with radially extending vanes that rotate in a pump ring when driven by pressurized fluid provided to port 109d or port HOd. The vanes may have variable lengths and may be biased to maintain contact with the pump ring as they rotate. When fluid is driven between ports 109d and 1 lOd of hydraulic motor 102d, the vanes attached to rotor 107d are rotationally driven by the fluid to rotate, thereby rotating output shaft 108d. As shown, one side of valve 115d communicates with port 109d and fluid line 113d. The opposite side of valve 115d selectively communicates with pressure rail 51 via fluid line 116d and pressure rail 56 via fluid line 117d. One side of valve 120d communicates with port HOd and fluid line 121d. The opposite side of valve 120d selectively communicates with pressure rail 51 via fluid line 121 d and pressure rail 56 via fluid line 122d. Pump 50, pump 55 and hydraulic motor actuation unit lOOd form a hydrostatic transmission, so rotor 107a will rotate shaft 108d in direction 117d when fluid is drawn through fluid port 109d from line 113d and out through fluid port 1 lOd and into line 114d. Pump rotor 107d will rotate shaft 108d in direction 118d when fluid is drawn through fluid port HOd from line 114d and out through fluid port 109d and into line 113d. Based on relative pressure readings of sensors 54, 59, 11 Id and 112d, valve 115d may be operated to connect line 113d and port 109d to either rail 51 or 56 depending on desired pressure and valve 120d may be operated to connect line 114d and port 1 lOd to the other rail 51 or 56 depending again on desired pressure.

[0059] As shown with reference to FIG. 10, shaft 108d of actuation unit lOOd may be operated to rotate in a direction 17d when valve 115d is open to the high pressure and fluid enters in through port 109d from line 113a and exits out through port HOd into line 114d. Based on relative pressure readings of sensors 54, 59, 11 Id and 112d, valve 115d may be operated to connect line 113d and port 109d to either rail 51 or 56 depending on which is at a greater pressure (the high pressure rail) and valve 120d may be operated to connect line 114d and port 1 lOd to the other rail 51 or 56 that is at a lower pressure (the low pressure rail). As shown with reference to FIG. 11,shaft 108d of actuation unit lOOd may be operated to rotate in the opposite direction 18d when valve 120d is open to the high pressure and fluid exits out through port 109d to line 113d and enters in through port HOd from line 114d. Thus, to provide a desired flow and pressure differential on rotor 107d, valves 115d and 120d may be operated to connect to a desired pressure differential between rails 51 and 56.

[0060] Other types of hydraulic motors may be used as alternatives, including without limitation radial-piston type hydraulic motors, axial-piston type hydraulic motors, and gear-type hydraulic motors in which hydraulic pressure is transformed into torque. For example, and without limitation, a radial-piston type hydraulic motor may be employed. Such a motor may comprise a plurality of radially positioned pistons disposed in cylinders in a cylinder block that is connected to an output shaft and rotates relative to a cam.

[0061] As shown in FIG. 2, each of actuator units lOOe and lOOf share a common configuration. Actuation units lOOe and lOOf generally includes rotary hydraulic motors 102e and 102f, single unit four-way valves 115e and 115f, pressure sensors l l le and 11 If, pressure sensors 112e and 112f, and safety valves 127e and 127f, 128e and 128f and 129e and 129f, respectively. Hydraulic piston assemblies 102e and 102f each generally have the same configuration and functionality as hydraulic piston assembly 102d. Pressure sensors l l le and 11 If and 112e and 112f generally have the same configuration and functionality as pressure sensors I l la and 112a, respectively. Valves 115e and 115f each generally have the same configuration and functionality as four- way valve 115g. In this embodiment, actuation units lOOe and 1 OOf are not utilized to provide regenerative power to system 15, thereby reducing complexity in the control of system 15 by controller 41.

[0062] Referring now to FIGS. 12 and 13, an alternative electric powered actuator system 215 for a mobile machine is provided. In this embodiment, the mobile machine is a skid steer loader 220 and electric powered actuator system 215 actuates parallel lift cylinders 202a and parallel tilt cylinders 202b of bucket 229 of skid steer loader 220 relative to body 217 of skid steer loader 220. In this embodiment, electric powered actuator system 215 also provides an accessory cylinder 202c for actuating accessory implements. As with system 15, system 215 may be employed in a variety of other applications, including without limitation in excavators, wheel loaders and in other mobile equipment or machines that require multiple actuation elements.

[0063] As shown in FIG. 13, system 215 generally has the same configuration and functionality of system 15 shown in FIG. 2. However, in this embodiment, system 215 of mobile machine 220 controls only three separate control axes or degrees of freedom. Linear actuation unit 200a provides linear motion on axis 203a and controls actuation of lift arms 226 relative to frame 217 about axis 201 and linear actuation unit 200b provides linear motion on axis 203b and controls actuation of bucket 229 relative to arms 226 about axis 201b. Auxiliary actuation unit 200c is an accessory cylinder for actuating accessory or auxiliary implements or tools.

[0064] Hydraulic pressure control rail lines 251 run from pump 250 to each of actuator units 200a-200c, and hydraulic pressure control rail lines 256 run from pump 255 to each of actuator units 200a-200c. Pressure sensor 254 is in control line 251 between pump 250 and actuator units 200a-200c and pressure sensor 259 is in control line 256 between pump 255 and actuator units 200a-200c. Hydraulic tank line 261 runs between pump 250 and tank 260, and hydraulic tank line 262 runs between pump 255 and tank 260.

[0065] System controller 241 is connected to battery system 240 and receives power from battery system 240. System controller 241 communicates with drive electronics 242 to supply a current of the appropriate magnitude and polarity to motor 245. Controller 241 receives drive commands and feedback from sensors in system 215, such as sensors 254, 259, 21 la-211c, and 212a-212c, and controls motor 245 and valves 215a-215c, 220a-220c and 227a-127c, accordingly. Thus, pressure transducers and position transducers in system 215 may be fed back to motor controller 241.

[0066] Power or battery system 240 also includes a regenerative power circuit to take advantage of a regenerative mode described below in which pump 250 or pump 255 and motor 245 are controlled to operate as a generator in a power generation mode when external regenerative forces, such as gravity loads, on hydraulic actuators 202a-202c exceed a threshold drive pressure differential of pumps 250 and 255 and drive torque of motor 245.

[0067] In this embodiment, pumps 250 and 255 are each 4-quadrant variable speed bidirectional or reciprocating internal two-port pumps that can each operate as a pump and also as a motor. Motor 245 is a brushless D.C. variable-speed servo-motor that is supplied with a current via power source 240 and drive electronics 242. Valves 215a-215c and 220a-220c are each three-way three-port three-position solenoid valves controlled by controller 241.

[0068] As shown in FIG. 13, each of actuator units 200a, 200b, and 200c share a common configuration that is substantially the same as actuation unit 100a. Thus, each actuation unit 200a- 200c generally includes hydraulic piston assemblies 202a-202c, three-way valves 215a-215c, three-way valves 220a-220c, pressure sensors 21 la-211c, pressure sensors 212a-212c, and safety valves 227a-227c, 228a-228c and 229a-229c, respectively.

[0069] Hydraulic piston assemblies 202a-202c include pistons 207a-207c slidably disposed within cylindrical housings 204a-204c such that pistons 207a-207c may be driven in both directions, with one side of valves 215a-215c communicating with cylinder chambers 205a-205c via ports 209a-209c and fluid lines 213a-213c and the opposite side of valves 215a-215c selectively communicating with pressure rail 251 via fluid lines 216a-216c and pressure rail 256 via fluid lines 217a-217c, respectively. One side of valves 220a-220c communicate with chambers 206a-206c via ports 210a-210c and fluid lines 214a-214c and the opposite side of valves 220a-220c selectively communicate with pressure rail 251 via fluid lines 221a-221c and pressure rail 256 via fluid lines 222a-222c, respectively. Pump 250, pump 255 and piston actuation units 200a-200c form a hydrostatic transmission, so pistons 207a-207c will extend and retract rods 208a-208c depending on the pressure differential on each side of pistons 207a-207c, respectively.

[0070] Rod 208a of actuation unit 200a may be operated to extend when pressure on the chamber 205a side face of piston 207a is greater than pressure on the opposite chamber 206a side face of piston 207a and may be operated to retract when pressure on the chamber 205a side face of piston 207a is less than pressure on the opposite chamber 206a side face of piston 207a. Based on relative pressure readings of sensors 254, 259, 211a and 212a, valve 215a may be operated to connect line 213a and chamber 205a to either rail 251 or 256 and valve 220a may be operated to connect line 214a and chamber 206a to the other rail 251 or 256, all depending on the desired pressure differential. Similarly, rod 208b of actuation unit 200b may be operated to extend when pressure on the chamber 205b side face of piston 207b is greater than pressure on the opposite chamber 206b side face of piston 207b and may be operated to retract when pressure on the chamber 205b side face of piston 207b is less than pressure on the opposite chamber 206b side face of piston 207b. Based on relative pressure readings of sensors 254, 259, 211b and 212b, valve 215b may be operated to connect line 213b and chamber 205b to either rail 251 or 256 and valve 220b may be operated to connect line 214b and chamber 206b to the other rail 251 or 256,all depending on the desired pressure differential. Similarly, rod 208c of actuation unit 200c may be operated to extend when pressure on the chamber 205c side face of piston 207c is greater than pressure on the opposite chamber 206c side face of piston 207c and may be operated to retract when pressure on the chamber 205c side face of piston 207c is less than pressure on the opposite chamber 206c side face of piston 207c. Based on relative pressure readings of sensors 254, 259, 211c and 212c, valve 215c may be operated to connect line 213c and chamber 205c to either rail 251 or 256 and valve 220c may be operated to connect line 214c and chamber 206c to the other rail 251 or 256, all depending on the desired pressure differential.

[0071] In addition, each of actuator units 200a, 200b and 200c are configured to operate in tandem with each other such that, based on relative pressure readings of sensors 254, 259, 21 la- 2110, and 212a-212c, the load conditions, and the operating commands, valve 215a may be operated to block or connect line 213a and chamber 205a to either rail 251 or 256, valve 220a may be operated to block or connect line 214a and chamber 206a to either rail 251 or 256, valve 215b may be operated to block or connect line 213b and chamber 205b to either rail 251 or 256, valve 220b may be operated to block or connect line 214b and chamber 206b to either rail 251 or 256, valve 215c may be operated to block or connect line 213c and chamber 205c to either rail 251 or 256, and valve 220c may be operated to block or connect line 214c and chamber 206c to either rail 251 or 256. And under certain load conditions, system 215 may be configured to operate pump 255 as a hydraulic drive pump and to operate pump 250 as a regenerative motor, to operate pump 250 as a hydraulic drive pump and to operate pump 255 as a regenerative motor, to operate both pump 250 and pump 255 as hydraulic drive pumps, or to operate both pump 250 and pump 255 as regenerative motors.

[0072] For example and without limitation, with system 215, when hydraulic actuator 202a is driven to extend opposite to a first external force, hydraulic actuator 202b is driven to retract with a second external force, and hydraulic actuator 202c is driven to retract with a third external force, via controller 41, (i) valve 215a may operatively connect actuator port 209a to pressure rail 256 to drive hydraulic actuator 202a opposite to the first external force, (ii) valve 220a may operatively connect actuator port 210a to low pressure rail 251, (iii) valve 215b may operatively connect actuator port 209b to pressure rail 256 when pressure at actuator port 209b is higher relative to pressure rail 256 to help drive hydraulic actuator 202a, (iv) valve 220b may operatively connectactuator port 210b to low pressure rail 251, (v) valve 215c may operatively connect actuator port 209c to pressure rail 256 when pressure at actuator port 209c is higher relative to pressure rail 256 to help drive hydraulic actuator 202a, and (vi) valve 220c may operatively connect actuator port 210c to low pressure rail 251.

[0073] As another example and without limitation, when hydraulic actuator 202a is driven opposite to a first external force, hydraulic actuator 202b is driven to retract with a second external force, and hydraulic actuator 202c is driven to retract with a third external force, via controller 41, (i) valve 215a may operatively connect actuator port 209a to pressure rail 256 to drive hydraulic actuator 202a opposite to the first external force, (ii) valve 220a may operatively connect actuator port 210a to low pressure rail 251, (iii) valve 215b may operatively connect actuator port to low pressure rail 251 when pressure at actuator port 209b is higher relative to pressure rail 251 and pump 250 may be operated in a regenerative mode as a motor, (iv) valve 220b may operatively connect actuator port 210b to pressure rail 251, (v) valve 215c may operatively connect actuator port 209c to pressure rail 251 when pressure at actuator port 209c is higher relative to pressure rail 251 with pump 250 further operated in a regenerative mode as a motor, and (vi) valve 220c may operatively connect actuator port 210c to pressure rail 251.

[0074] Thus, in this embodiment power source 240 includes a regenerative power circuit to take advantage of a regenerative mode in which pumps 250 and / or 255 and motor 245 are controlled to operate as a generator in a power generation mode when external regenerative forces, such as gravity loads, on hydraulic assemblies 200a, 200b or 200c exceed a threshold drive pressure differential of pumps 250 and / or 255 and drive torque of motor 245. When bucket 229 and / or other accessories of skid steer 220 need to absorb gravitational forces and impact forces, pumps 250 and / or 255 and motor 245 may be configured to operate as electric generator that converts torque generated from such forces on the system into electricity that is used directly or stored in battery storage 240. For example, the effects of gravity when bucket 229 is raised will generate a force on pistons 207a of hydraulic actuator 202a, which in turn produces pressure on pump 250 or 255 when brake 227a is not activated, which in turn produces a torque on the shaft of servomotor 245. Under these conditions and in the regenerative mode, electric motor 245 is configured to act as an electric generator. Thus, actuator system 215 includes regenerative energy functionality.

[0075] Actuation systems 15 and 215 provide a number of benefits. The systems allow for variable speed actuation and full control of the location of the actuators within their range of motion. In the systems, regenerative power from gravity loads can be transferred back to the power supply and high shock loading and extreme impacts to the bucket or other tools are absorbed. Since each axis has independent meter-in and meter-out valves, multiple actuators can be run at the same time off a single pump. The systems can handle extreme impact, do not require sensitive electromechanical solutions, and the actuator cylinders in the systems are easy to replace. The systems do not require either a closed system charged tank or a tank line charge pump system to overcome cavitation issues. The systems have high energy efficiency that minimizes the size of the battery pack. The systems allow for high dynamic response of 16 milliseconds step response and 100 Hz frequency response at + / - 5% signal, performance that allows for autonomous operation.

[0076] It should be appreciated that certain features of the system, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable combination. While various embodiments have been described in detail above, it should be understood that they have been presented by way of example, and not limitation. While the presently preferred form of an improved electric powered actuator system for mobile machines has been shown and described, and several modifications thereof discussed, persons skilled in this art will readily appreciate that various additional changes and modifications may be made without departing from the scope of the invention, as defined and differentiated by the claims.

Claims

CLAIMSWhat is claimed is:

1. A mobile machine comprising: a first element configured to be driven relative to a body portion of said mobile machine by a first hydraulic actuator; said first hydraulic actuator configured to actuate said first element to be driven relative to said body portion of said mobile machine within a first range of motion; said first hydraulic actuator comprising a first actuator port and a second actuator port; a tank; a first four-quadrant pump connected to said tank; a second four-quadrant pump connected to said tank; an electric power source; an electric motor connected to said electric power source and configured to be supplied with a current; said motor connected to at least one of said first four-quadrant pump and said second four-quadrant pump; a hydraulic system extending between said first hydraulic actuator and said tank; said hydraulic system comprising a first pressure rail and a second pressure rail; said first pressure rail connected to said first four-quadrant pump and said second pressure rail connected to said second four-quadrant pump; a first valve between said first actuator port of said first hydraulic actuator and both said first pressure rail and second pressure rail and operatively configured to meter flow between said first pressure rail, said second pressure rail, and said first actuator port of said first hydraulic actuator; a second valve between said second actuator port of said first hydraulic actuator and both said first pressure rail and second pressure rail and operatively configured to meter flow between said first pressure rail, said second pressure rail, and said second actuator port of said first hydraulic actuator;a second element configured to be driven relative to said body portion of said mobile machine by a second hydraulic actuator; said second hydraulic actuator configured to actuate said second element to be driven relative to said body portion of said mobile machine within a second range of motion; said second hydraulic actuator comprising a third actuator port and a fourth actuator port; said hydraulic system extending between said second hydraulic actuator and said tank; a third valve between said third actuator port of said second hydraulic actuator and both said first pressure rail and second pressure rail and operatively configured to meter flow between said first pressure rail, said second pressure rail, and said third actuator port of said second hydraulic actuator; a fourth valve between said fourth actuator port of said second hydraulic actuator and both said first pressure rail and second pressure rail and operatively configured to meter flow between said first pressure rail, said second pressure rail, and said fourth actuator port of said second hydraulic actuator; wherein actuation of said first object to be driven relative to said body portion of said mobile machine within said first range of motion is operatively controllable and actuation of said second object to be driven relative to said body portion of said mobile machine within said second range of motion is operatively controllable.

2. The mobile machine set forth in claim 1 , wherein said first hydraulic actuator comprises a first housing having said first actuator port and said second actuator port.

3. The mobile machine set forth in claim 2, wherein said first hydraulic actuator comprises a linear hydraulic actuator or a rotary hydraulic actuator.

4. The mobile machine set forth in claim 3, wherein: said hydraulic actuator comprises a linear hydraulic actuator; said housing comprises a hydraulic cylinder having a first hydraulic chamber and a second hydraulic chamber;said linear hydraulic actuator comprises a hydraulic piston between said first hydraulic chamber and said second hydraulic chamber and an actuating rod connected to said piston and configured to translate along an axis with movement of said piston relative to said housing; and one of said housing or said actuating rod is connected to said mobile machine and the other of said housing or said actuating rod is connected to said element to be driven.

5. The mobile machine set forth in claim 3, wherein: said hydraulic actuator comprises a rotary hydraulic actuator; said rotary hydraulic actuator comprises a hydraulic motor: said hydraulic motor comprises a hydraulic rotary element between said first actuator port and said second actuator port of said first housing and an actuating shaft connected to said rotary element and configured to rotate about an axis with movement of said rotary element relative to said housing; and one of said housing or said actuating shaft is connected to said mobile machine and the other of said housing or said actuating shaft is connected to said element to be driven.

6. The mobile machine set forth in claim 5, wherein said hydraulic motor is selected from a group consisting of a vane-type hydraulic motor, a radial-piston type hydraulic motor, an axial-piston type hydraulic motor, and a gear-type hydraulic motor.

7. The mobile machine set forth in claim 1, wherein said range of motion comprises rotational motion about a rotational axis or translational motion along a translation axis.

8. The mobile machine set forth in claim 1, comprising a battery supplying said current to said electric motor.

9. The mobile machine set forth in claim 1, wherein said motor is connected to both said first four-quadrant pump and said second four-quadrant pump.

10. The mobile machine set forth in claim 1, wherein said first four-quadrant pump comprises a first bidirectional pump connected to said electric motor and said second four- quadrant pump comprises a second bidirectional pump connected to a second electric motor.11 . The mobile machine set forth in claim 1 , wherein said first valve comprises a first three-way valve assembly and said second valve comprises a separate second three-way valve assembly.

12. The mobile machine set forth in claim 1, wherein said first valve and said second valve are in a single four-way valve assembly.

13. The mobile machine set forth in claim 1, wherein mobile machine comprises an excavator or a skid steer loader and said element to be driven comprises a bucket configured to be lifted and tilted relative to said body portion of said mobile machine.

14. The mobile machine set forth in claim 1, wherein said tank is open to atmosphere.

15. The mobile machine set forth in claim 1, comprising a controller that receives input signals and outputs command signals to said electric motor, said first valve, and said second valve to control actuation of said object to be driven relative to said body portion of said mobile machine.

16. The mobile machine set forth in claim 15, comprising: a first rail sensor configured to sense a pressure of said first pressure rail and to provide a pressure input signal to said controller; a second rail sensor configured to sense a pressure of said second pressure rail and to provide a pressure input signal to said controller; a first actuator sensor configured to sense a pressure of said first actuator port and to provide a pressure input signal to said controller; a second actuator sensor configured to sense a pressure of said second actuator port and to provide a pressure input signal to said controller; a third actuator sensor configured to sense a pressure of said third actuator port and to provide a pressure input signal to said controller; and a fourth actuator sensor configured to sense a pressure of said fourth actuator port and to provide a pressure input signal to said controller.

17. The mobile machine set forth in claim 16, wherein said controller receives input signals from said first rail sensor, said second rail sensor, said first actuator sensor, said second actuator sensor, said third actuator sensor, and said fourth actuator sensor and outputs command signals to said electric motor, said first valve, and said second valve as a function of said input signals from said first rail sensor, said second rail sensor, said first actuator sensor, said second actuator sensor, said third actuator sensor, and said fourth actuator sensor.

18. The mobile machine set forth in claim 15, comprising a regenerative power stage to said electric motor and wherein said electric motor is controlled by said controller to operate in a regeneration mode.

19. The mobile machine set forth in claim 1, comprising: a third element configured to be driven relative to said body portion of said mobile machine by a third hydraulic actuator; said third hydraulic actuator configured to actuate said third element to be driven relative to said body portion of said mobile machine within a third range of motion; said third hydraulic actuator comprising a fifth actuator port and a sixth actuator port; said hydraulic system extending between said third hydraulic actuator and said tank; a fifth valve between said fifth actuator port of said third hydraulic actuator and both said first pressure rail and second pressure rail and operatively configured to meter flow between said first pressure rail, said second pressure rail, and said fifth actuator port of said third hydraulic actuator; a sixth valve between said sixth actuator port of said third hydraulic actuator and both said first pressure rail and second pressure rail and operatively configured to meter flow between said first pressure rail, said second pressure rail, and said sixth actuator port of said third hydraulic actuator; wherein actuation of said third object to be driven relative to said body portion of said mobile machine within said third range of motion is operatively controllable.

20. A mobile machine comprising:a plurality of elements configured to be driven relative to a body portion of said mobile machine; a plurality of hydraulic actuator units configured to actuate said plurality of elements to be driven relative to said body portion of said mobile machine; a tank; a first four-quadrant pump connected to said tank; a second four-quadrant pump connected to said tank; an electric power source; an electric motor connected to said electric power source and configured to be supplied with a current; said motor connected to at least one of said first four-quadrant pump and said second four-quadrant pump; a hydraulic system extending between said plurality of actuator units and said tank; said hydraulic system comprising a first pressure rail and a second pressure rail; said first pressure rail connected to said first four-quadrant pump and said second pressure rail connected to said second four-quadrant pump; and each of said plurality of hydraulic actuators comprising: a first actuator port and a second actuator port; a first valve between said first actuator port and both said first pressure rail and second pressure rail and operatively configured to meter flow between said first pressure rail, said second pressure rail, and said first actuator port; and a second valve between said second actuator port and both said first pressure rail and second pressure rail and operatively configured to meter flow between said first pressure rail, said second pressure rail, and said second actuator port.

21. The mobile machine set forth in claim 20, comprising a controller in communication with said motor and said first and said second valves of each of said actuator units and wherein said first valve and said second valve of each of said actuator units meter flow between said first actuator port and said second actuator port and said first rail and said second rail as a function of a control signal from said controller.

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