Linear actuator based travel control

Abstract

A work machine includes a load bucket and an operator controller for controlling a position of the load bucket. The work machine may include an actuator assembly coupled to hold a load bucket in a position based on a signal from an operator controller. The actuator assembly may include a motor and a brake assembly. The brake assembly may include a non-spring coupled brake and a spring coupled brake. The work machine may also include a control circuit coupled to the actuator assembly to actuate the spring-coupled brake in response to detecting that the non-spring-coupled brake remains stationary in the load bucket. The control circuit may further control the motor to apply the additional braking force when the amplitude of oscillation of the work machine is detected to exceed a threshold amplitude based on a damping coefficient of the spring coupled brake.

Description

Technical Field

[0001] This document relates to motion control on work machines and, more particularly, to techniques for reducing or eliminating oscillations and other unwanted mechanical motions during travel of the work machine over uneven terrain. Background Art

[0002] During work machine operation, some work machines, such as wheeled load machines, may travel with a loaded work tool over uneven terrain. During travel, the work machine may "oscillate" or "bounce" in one or more directions, resulting in reduced operator comfort and safety issues due to difficulty controlling the work machine. In some cases, the oscillations may become so intense that the operator must reduce the ground speed of the work machine, resulting in inefficiencies and increased costs in the operation of the work machine. Some available wheeled load machines are equipped with a ride control system that hydraulically connects the load-bearing side of the lift cylinder to a hydraulic accumulator. The accumulator and associated lines and orifices allow the linkage to move gently up and down and act as a spring / damper system that is adjusted to dampen machine oscillations. However, some modern systems today replace these hydraulic cylinders with linear actuators, which rigidly hold the load / loaded work tool and do not provide the function of controlling machine oscillations.

[0003] US Patent No. 8,930,052 discusses a control system for a drive system for a mobile device, wherein an electric traction motor is controlled by a torque controller to provide uniform torque. Summary of the invention

[0004] Work machines often travel over uneven terrain with a loaded work implement. On uneven terrain, the machine may begin to bounce. Excessive bouncing makes the machine difficult to operate, and the operator must slow the machine sufficiently to dampen the oscillations. Some available wheeled load machines include a ride control system that hydraulically connects the load-bearing side of the lift cylinder to a hydraulic accumulator to lift the load using a lift linkage, thereby acting as a damper for machine oscillations. However, some work machines do not include a hydraulic lift cylinder, but instead use a linear actuator to control the lift.

[0005] To address these and other issues, an exemplary work machine may include a load bucket and an operator controller for controlling a position of the load bucket. The work machine may also include an actuator assembly coupled to the load bucket and configured to maintain the load bucket in a position based on a signal from the operator controller. The actuator assembly may include a motor and a brake assembly. The brake assembly may include a non-spring coupled brake and a spring coupled brake. A control circuit coupled to the actuator assembly may activate the spring coupled brake in response to detecting that the non-spring coupled brake is holding the load bucket stationary. When an oscillation amplitude of the work machine is detected to exceed a threshold amplitude based on a damping coefficient of the spring coupled brake, the control circuit may control the motor to apply an additional braking force. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a front view showing an example working machine according to the present invention.

[0007] Figure 2 is a perspective view of a linear actuator according to the present invention.

[0008] Figure 3 is a block diagram of components of a travel control according to the present invention.

[0009] Figure 4 is a flow chart of a method for providing driving control according to the present invention.

[0010] Figure 5 is a computer system upon which example embodiments may be implemented. DETAILED DESCRIPTION

[0011] Examples according to the present invention relate to control circuitry for monitoring various parameters of a work machine as the work machine travels over terrain. As the work machine moves, oscillations may occur. These oscillations may cause discomfort to the operator of the work machine and make it difficult for the operator of the work machine to control machine operation.

[0012] Figure 1 An example machine 100 according to the present invention is shown. Figure 1 In the embodiment of the present invention, machine 100 includes a frame 102, wheels 104, implements 106, and a speed control system implemented in one or more onboard electronic devices, such as an electronic control unit or ECU 108. The example machine 100 is a wheeled load machine. However, in other examples, the machine can be other types of machines associated with various industries, including, for example, construction, agriculture, forestry, transportation, material handling, waste management, etc. Therefore, although multiple examples are described with reference to wheeled load machines, examples according to the present invention can also be applied to other types of machines, including graders, scrapers, bulldozers, excavators, compactors, material transporters such as dump trucks, and other example machine types.

[0013] The machine 100 includes a frame 102 mounted on four wheels 104, although in other examples, the machine may have more or less than four wheels. The frame 102 is configured to support and / or mount one or more components of the machine 100. For example, the machine 100 includes a housing 110 coupled to the frame 102. Among other components, the housing 110 may house an electric motor to propel the machine over various terrains via the wheels 104. In some examples, multiple electric motors are included in multiple housings at multiple locations of the machine 100.

[0014] The machine 100 includes an implement 106 coupled to the frame 102 via a linkage assembly 112 that is configured to be actuated to articulate a bucket 114 of the implement 106. The bucket 114 of the implement 106 may be configured to transfer material, such as soil or debris, from one location to another. The linkage assembly 112 may include one or more cylinders 116 that are configured to be actuated, for example, hydraulically or pneumatically, to articulate the bucket 114. For example, the linkage assembly 112 may be actuated by the cylinders 116 to raise and lower and / or rotate the bucket 114 relative to the frame 102 of the machine 100. An actuator 117 (e.g., an electric linear actuator (ELA)) may be provided to hold the weight of the linkage (e.g., the weight of the material within the bucket 114) rather than a hydraulic cylinder, such as provided at 116. For example, the actuator 117 may be used to hold the bucket 114 in an appropriate position (e.g., as Figure 1 1). The bucket 114 may oscillate at an angle as shown at 118, be raised to a height 120, etc.

[0015] The platform 122 is coupled to the frame 102 and provides access to various locations on the machine 100 for operation and / or maintenance purposes. The machine 100 also includes an operator compartment 124, which may be open or enclosed and accessible via the platform 122. The operator compartment 124 may include one or more control devices 126, such as joysticks, steering wheels, pedals, levers, buttons, switches, etc. The control devices 126 are configured to enable an operator to control the machine 100 and / or the implement 106. The operator compartment 124 may also include an operator interface, such as a display device, an audio source, a light source, or a combination thereof.

[0016] The machine 100 may be used in a variety of industrial, construction, commercial or other applications. The machine 100 may be operated by an operator in a cab 124 or by a remote operator. For example, the operator drives the machine 100 to and from different locations on a worksite and may also pick up and deposit loads of material using the bucket 114 of the implement 106. Autonomous operation is also possible. As an example, the machine 100 may be used to excavate a portion of a worksite by actuating the cylinder 116 or the actuator 117 to articulate the bucket 114 via the linkage 112 to dig into and remove dirt, rocks, sand, etc. from one portion of the worksite and deposit the load at another location.

[0017] During travel to or from a worksite or within a worksite, machine 100 may travel over uneven terrain with a work tool (e.g., bucket 114) loaded therein. For example, the work tool may be loaded with rocks, sand, dirt, etc. that have been removed or dug from the worksite or provided to the worksite. On uneven terrain, machine 100 may begin to oscillate along the X-axis or bounce along the Y-axis. Excessive bouncing makes the machine difficult to operate, and the operator must slow the machine sufficiently to suppress the oscillations.

[0018] Some machines 100 currently available may include a ride control system that hydraulically connects the load-bearing side of the lift cylinder to a hydraulic accumulator (e.g., along the location indicated at actuator 117). The accumulator (including any lines and orifices) may allow the linkage to move slightly up and down, thereby acting as a spring / damper system that is tuned to dampen oscillations of the machine 100. Such a ride control system is typically engaged when the ground speed of the machine 100 exceeds a threshold (e.g., over 10 mph, over 20 mph, or other manufacturer-specified ground speed).

[0019] However, some work machines 100 today may use actuators (e.g., linear actuators or electronic linear actuators (ELA)) instead of hydraulic cylinders, and may also provide travel control for these work machines 100. For example, the actuator may be similar to Figure 2 The actuator shown.

[0020] Figure 2 2 is a perspective view of a linear actuator 200 according to the present invention. The linear actuator 200 is shown as an example, and other similar types of actuators may be employed in various embodiments. For example, the actuator may include a rack and pinion actuator, a ball and screw actuator, and the like.

[0021] The actuator 200 may include a gearbox 212. The gearbox 212 may include a housing 214 that is mounted on one side to the linear unit 206 and on the other side to the motor adapter 210. The gearbox 212 may transfer the motor torque directly to the linear unit 206. The motor adapter 210 may include an AC induction motor, may run on battery power, and / or may include a brake (e.g., an electromagnetic brake, and in some examples, an additional centrifugal brake).

[0022] The ELA 200 (and similar ELAs in various other embodiments) can hold the load by using a mechanical brake on the motor shaft or an actuator mechanism that rigidly holds the load without energizing the motor. However, such rigid brakes do not provide a mechanism for the linkage to move during travel, and therefore there may be machine oscillation or "bounce" which increases operator discomfort and makes it difficult for the operator to control the machine.

[0023] Systems and methods according to embodiments address these and other problems by providing different operating modes for the ELA, which provide different types or sources of braking based on criteria such as ground speed, load, oscillation amplitude, and other variables. Figure 3 Circuit components are described to perform or control different operating modes.

[0024] Figure 3 300 can provide control signals, and the apparatus for travel control can include an actuator assembly and a control circuit as described below. For example, the actuator assembly can include a linear actuator mechanism 302, as described above with reference to Figure 2 The example ELA is described above. Figure 2 As described above, the motor 304 may be associated with the linear actuator mechanism 302. For example, the motor 304 may include some or all of the components of the motor adapter 210, or may be coupled to the motor adapter 210 ( Figure 2 ). Also as described above, the motor brake 306 may be provided in assembly with the motor 304 .

[0025] In an embodiment, a compression coupling (e.g., spring coupling) brake 308 is added for motion damping under the following conditions and according to the following criteria. The brake 308 may include a compression element or a spring (e.g., a torsion spring, but the embodiment is not limited thereto) between the brake 306 and the motor shaft of the motor 304. The brake 308 may allow the motor shaft to oscillate freely around a center position. In summary, the motor brake 306 (e.g., a non-spring coupled brake), the brake 308 (e.g., a spring coupled brake), and the motor 304 may be referred to as an actuator assembly 310.

[0026] Figure 3 Some or all of the components shown in FIG. 1 may be coupled to the load bucket 114 ( Figure 1 ) based on information from an operator controller (e.g., controller 126 ( Figure 1 )) signal to hold the load bucket 114 in one position. When the brake is not applied (e.g., when Figure 2 The control circuit 300 may execute a control algorithm (e.g., in software or firmware) to determine the motor torque of the motor described in the example above to maintain the load. The algorithm may be used Figure 3 The circuit and signals shown are used to monitor the output motor torque and speed to measure the amplitude and frequency of oscillation in real time.

[0027] For example, the control circuit 300 may provide a signal 312 to control the current 314 and other parameters of the motor 304. The control circuit 300 may achieve this control by providing the signal 312 to an inverter 316. The inverter 316 may control the frequency of the power provided to the motor 304 to control the speed of the motor 304. Without the inverter 316, once power is provided to the motor 304, the motor 304 will run at full speed.

[0028] The inverter 316 may provide feedback 318 to the control circuit 300. The feedback 318 may include, for example, parameters of the motor force of the motor 304. The linear actuator mechanism 302 may provide actuator position and velocity information to the inverter 316 using a signal 320. Additionally or alternatively, the linear actuator mechanism 302 may provide actuator position and velocity information to the control circuit 300 using a signal 322. The control circuit 300 may also control the brakes 306, 308 by providing solenoid commands 324, 326, respectively.

[0029] In some embodiments, Figure 3 Other circuits or devices not shown in the figure can provide information to the control circuit 300. For example, the oscillation of the machine can be measured by an inertial measurement unit including, for example, an accelerometer and a gyroscope. In some examples, the control circuit 300 can use the signal 312 to update the motor torque command at each moment in time to offset and damp the oscillation.

[0030] In some embodiments, when the brakes are applied (e.g., when Figure 2 The non-spring coupled brake 306 will typically be applied using the solenoid command 324 when the motor torque of the exemplary motor described in FIG. 3 is not holding the load. The spring coupled brake 308 may be applied according to Figure 4 The algorithm shown is applied gradually.

[0031] Figure 44 is a flow chart of a method 400 for providing ride control using a spring coupled brake 308 according to the present invention. The method 400 may begin at operation 402, where ride control is in an "off" state, such as when ride control is not desired due to ground speed being below a threshold. Other threshold parameters may be used to determine when ride control is desired or should be activated. At operation 402, as described above, prior to achieving ride control, the non-spring coupled brake 306 may be applied, and the motor torque of the motor associated with the ELA will generally not hold the load.

[0032] When the ground speed exceeds a threshold, it may be desirable to engage in ride control to increase operator comfort and control. In operation 404, the control circuit 300 may, for example, be based on the controller 126 ( Figure 1 ) to detect whether braking is required. In the absence of an operator command at the controller 126, the desired braking is as follows Figure 4 The method 400 is shown starting at operation 406 in the left branch.

[0033] At operation 406, the control circuit 300 may perform a balancing operation to gradually switch from using the non-spring coupled brake 306 to using the spring coupled brake 308. In some examples, activation of the spring coupled brake 308 may occur in response to (or upon) detecting that the non-spring coupled brake 306 is holding the load stationary. For example, if the operator does not execute a command (as determined at operation 404), the control circuit 300 may determine that the non-spring coupled brake 306 is holding the load stationary. The speed at which this switching occurs may be limited or controlled, with the end result that the spring coupled brake 308 is eventually applied at operation 408. During operation 406, the spring coupled brake 308 is gradually applied, while the non-spring coupled brake 306 is gradually released. During this balancing operation, the load may drop slightly until the load is caught by the spring coupled brake 308, and during this time, the motor 304 control may be applied to hold the load steady.

[0034] The control circuit 300 may monitor the signal 318 ( Figure 3) to detect how much motor force is being used to support the load (e.g., whether the load is fully supported by the motor force can be used to determine how much of the load has been transferred to the spring-coupled brake 308). Once the motor force drops to zero or approximately zero, the control circuit 300 can determine that the spring-coupled brake 308 is bearing the entire load (e.g., fully supporting the load). The control circuit 300 (or other control circuits of the machine 100) can use the spring-coupled brake 308 to perform position control of the load after this balancing is completed. Parameters that provide position control can be saved or updated. For example, filters and constants of a proportional-integral-derivative (PID) controller used to provide position control will then be updated or determined based on the spring-coupled brake rather than the motor 304. After determining that the spring-coupled brake 308 is bearing the entire load, the control circuit 300 can monitor oscillations of the work machine (e.g., using an accelerometer, etc.). If the amplitude of these oscillations or other movements is detected to be above a threshold, the control circuit 300 can use other brakes (e.g., non-spring-loaded brakes 306) to apply additional braking force to suppress the oscillations.

[0035] At operation 410, the motor 304 can be used for damping when the motor force is zero and the spring-coupled brake 308 supports the entire load. When the motor 304 is used for damping, energy can be recovered from the motor 304 and enter the motor power source or used for other electrical purposes of the machine 100. Therefore, operation 412 reflects a state in which the spring-coupled brake 308 holds the load and the motor provides damping and energy recovery power generation, resulting in some additional energy recovery. Once operation 412 has been reached or achieved, when the ground speed decreases, the travel control can be turned off, the non-spring-coupled brake 306 can be applied, and the spring-coupled brake 308 can be deactivated (e.g., operation can be restarted at operation 402). Otherwise, the machine 100 can be held at operation 412.

[0036] Alternatively, if the load is supported by the spring-coupled brake 308 and braking is no longer desired (e.g., if bucket 114 movement is desired), the operation may change to the right side of the flowchart with operation 414. Operation 414 may generally be performed when travel control is desired and the non-spring-coupled brake 306 is to be "off," such as if a small bucket "lift" is desired when the machine 100 is moving at travel speed. Thus, at operation 416, the non-spring-coupled brake 306 is released (e.g., the control circuit 300 may provide a solenoid command 324 to close the non-spring-coupled brake 306). Thereafter, in addition to providing oscillation damping, at operation 418, the motor 304 will hold the entire load. If bucket movement is not desired, the operation may move to the left side of the flowchart at operation 406 to balance with the spring-coupled brake 308. Similarly, if the ground speed drops below the travel threshold, travel control may be removed and operation may resume at operation 402.

[0037] Figure 5 An example of a block diagram of a machine 500 is generally shown according to some embodiments, and any one or more of the techniques (e.g., methods) discussed herein can be performed on the machine. In an example, the machine 500 may include control circuitry or execute instructions associated with travel control and control of a starter solenoid to control a spring-coupled brake and motor associated with the ELA described herein. In alternative embodiments, the machine 500 may operate as a standalone device or may be connected (e.g., networked) to other machines. The machine 500 may serve as a control circuit 300, or perform one or more operations of the control circuit 300, or provide communication inputs or outputs from the control circuit 300 to a remote or local operator of the work machine 100.

[0038] As described herein, examples may include or may operate on logic or multiple components, modules or mechanisms. A module is a tangible entity (e.g., hardware) that can perform a specified operation when in operation. A module includes hardware. In one example, the hardware may be specifically configured to perform a specific operation (e.g., hardwired). In one example, the hardware may include a configurable execution unit (e.g., a transistor, a circuit, etc.) and a computer-readable medium containing instructions, wherein the instructions configure the execution unit to perform a specific operation at runtime. Configuration may occur under the guidance of the execution unit or a load mechanism. Therefore, when the device is operating, the execution unit is communicatively connected to the computer-readable medium. In this example, the execution unit may be a member of more than one module. For example, in operation, the execution unit may be configured by a first set of instructions to implement a first module at a point in time, and reconfigured by a second set of instructions to implement a second module.

[0039] The machine (e.g., computer system) 500 may include a hardware processor 502 (e.g., a central processing unit (CPU), a graphics processing unit (GPU), a hardware processor core, or any combination thereof), a main memory 504, and a static memory 506, some or all of which may communicate with each other via an interconnect (e.g., a bus) 508. The machine 500 may also include a display unit 510, an alphanumeric input device 512 (e.g., a keyboard), and a user interface (UI) navigation device 514 (e.g., a mouse). In one example, the display unit 510, the alphanumeric input device 512, and the UI navigation device 514 may be a touch screen display. The machine 500 may additionally include a storage device (e.g., a drive unit) 516, a signal generating device 518 (e.g., a speaker), a network interface device 520, and one or more sensors 521, such as a global positioning system (GPS) sensor, a compass, an accelerometer, or other sensors. The machine 500 may include an output controller 528, such as a serial (e.g., universal serial bus (USB), parallel or other wired or wireless (e.g., infrared (IR), near field communication (NFC), etc.) connection to communicate with or control one or more peripheral devices (e.g., printer, card reader, etc.).

[0040] The storage device 516 may include a non-transitory machine-readable (or computer-readable) medium 522 on which is stored one or more sets of data structures or instructions 524 (e.g., software) embodying or utilized by any one or more of the techniques or functionality described herein. The instructions 524 may also reside, completely or at least partially, within the main memory 504, within the static memory 506, or within the hardware processor 502 during execution of the instructions 524 by the machine 500. In one example, one or any combination of the hardware processor 502, the main memory 504, the static memory 506, or the storage device 516 may constitute a machine-readable medium.

[0041] Although machine-readable medium 522 is illustrated as a single medium, the term “machine-readable medium” may include a single medium or multiple media (eg, a centralized or distributed database, or associated caches and servers) configured to store one or more instructions 524 .

[0042] The term "machine-readable medium" may include any medium capable of storing, encoding, or carrying instructions for execution by the machine 500 and causing the machine 500 to perform any one or more of the techniques of the present invention, or capable of storing, encoding, or carrying data structures used by or associated with such instructions. Non-limiting examples of machine-readable media may include solid-state memory, and optical and magnetic media. Specific examples of machine-readable media may include: non-volatile memory, such as semiconductor memory devices (e.g., electrically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM)) and flash memory devices; magnetic disks, such as internal hard disks and removable disks; magnetic optical disks; and CD-ROM and DVD-ROM disks.

[0043] The instructions 524 may also be sent or received over the communication network 526 using a transmission medium via the network interface device 520 using any of a number of transmission protocols (e.g., frame relay, Internet Protocol (IP), transmission control protocol (TCP), user datagram protocol (UDP), hypertext transfer protocol (HTTP), etc.). Example communication networks may include a local area network (LAN), a wide area network (WAN), a packet data network (e.g., the Internet), a mobile phone network (e.g., a cellular network), a traditional telephone network, and a wireless data network (e.g., the Institute of Electrical and Electronics Engineers (IEEE) 802.11 family of standards, known as The IEEE 802.16 family of standards is known as ), IEEE 802.15.4 family of standards, peer-to-peer (P2P) networks, and the like. In one example, the network interface device 520 may include one or more physical jacks (e.g., Ethernet, coaxial, or telephone jacks) or one or more antennas connected to the communication network 526. In one example, the network interface device 520 may include multiple antennas for wireless communication using at least one of single-input multiple-output (SIMO), multiple-input multiple-output (MIMO), or multiple-input single-output (MISO) technology. The term "transmission medium" should be taken to include any intangible medium that can store, encode, or carry instructions for execution by the machine 500, and includes digital or analog communication signals or other intangible media to facilitate the communication of such software.

[0044] Industrial Applicability

[0045] In an example of operation of a work machine, some work machines may ride on rubber tires that bounce and cause discomfort and lack of control to the operator. Therefore, the system described herein, along with other braking systems, provides a spring-loaded brake in a linear actuator that is subject to a load (e.g., a load in a load bucket). In some cases, lift and load are provided by springs to allow for balancing and energy capture, thereby reducing bouncing and other undesirable motions.

[0046] The foregoing detailed description is intended to be illustrative rather than limiting. The scope of the present invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims

1. A working machine, comprising: Load bucket; operator controls for controlling the position of the load bucket; an actuator assembly coupled to the load bucket and configured to hold the load bucket in a position based on signals from the operator controls, the actuator assembly including a motor and a brake assembly including a non-spring coupled brake and a spring coupled brake; as well as a control circuit coupled to the actuator assembly, the control circuit being configured to: activating the spring coupled brake in response to detecting that the non-spring coupled brake is holding the load bucket stationary; and When it is detected that the amplitude of oscillation of the working machine exceeds a threshold amplitude, the electric motor is controlled to apply an additional braking force.

2. The work machine of claim 1, wherein the control circuit is configured to control the non-spring coupled brake to remove the braking force applied by the non-spring coupled brake upon detecting that the load is fully supported by the spring coupled brake. 3 . The work machine of claim 1 , wherein the spring coupled brake includes a compression element disposed between the non-spring coupled brake and a motor shaft of the electric motor to allow the motor shaft to oscillate. 4 . The work machine of claim 1 , wherein the control circuit is configured to detect a motor torque of the motor to determine whether the motor or the brake assembly is holding the load bucket stationary.

5. The work machine of claim 1, wherein the control circuit is configured to deactivate the spring coupled brake and activate the non-spring coupled brake when an operator control indicates that load bucket movement is to be initiated.

6. The work machine of claim 1, wherein the actuator comprises an electric linear actuator (ELA).

7. The work machine of claim 6, wherein the actuator assembly comprises a rack and pinion system or a ball and screw system.

8. The work machine according to claim 1, comprising: a ground speed detection circuit configured to detect a ground speed of the work machine, and wherein the control circuit refrains from activating the spring coupled brake until the ground speed exceeds a threshold value, and wherein the control circuit is configured to deactivate the spring coupled brake upon detecting that the ground speed has dropped below the threshold value.

9. The work machine of claim 1, wherein the control circuit is configured to control the brake assembly using a respective solenoid for each of the non-spring coupled brake and the spring coupled brake.

10. The work machine of claim 1 , wherein the control circuit is configured to, in response to detecting a motor torque level indicating that the motor is holding the load bucket stationary, control the motor to apply an additional braking force when an oscillation of the work machine exceeding the threshold amplitude is detected based on a damping coefficient of the spring-coupled brake.

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