Construction machine

Abstract

A construction machine with a pump, a pressure sensor that measures pressure, and a working cylinder with a retractable rod. The working cylinder has a bore chamber, a rod chamber, a bore chamber pressure sensor, bore pressure, a rod chamber pressure sensor, and rod pressure. The machine includes an input device that can be moved between neutral, extended, and retracted positions, and a sensor for measuring the position. The machine includes a control device programmed with an algorithm to control the movement of the working cylinder based on the detected position of the operator input device.The algorithm is designed to confirm that the pump pressure exceeds the bore-side chamber pressure as a prerequisite for setting a command which, in response to the detection of the operator input device in the rod extension position, controls the movement of the working cylinder to extend the rod.

Description

State of the art

[0001] The present disclosure relates to hydraulic systems for construction machinery. Brief description

[0002] The present disclosure, in one aspect, provides a construction machine including a pump, a pressure sensor, an operating cylinder, a downhole chamber pressure sensor, an operator input device, and a controller. The pressure sensor is configured to measure a pump pressure. The operating cylinder includes a rod operable to extend and retract. A downhole chamber of the operating cylinder is configured to be supplied with fluid from the pump during rod extension while fluid is removed from a rod-side chamber. The rod-side chamber of the operating cylinder is configured to be supplied with fluid from the pump during rod retraction while fluid is removed from the downhole chamber. The downhole chamber pressure sensor is configured to measure a downhole chamber pressure.The operator input device is movable between a neutral position, a rod extension position, and a rod retraction position. The operator input device includes a position sensor configured to measure the neutral position, the rod extension position, and the rod retraction position. The control device is communicatively coupled to the working cylinder and programmed with an algorithm configured to control the movement of the working cylinder based on the sensed position of the operator input device.

[0003] The algorithm is designed to confirm that the pump pressure exceeds the bore-side chamber pressure as a prerequisite for issuing a command that controls the movement of the actuator to extend the rod in response to the detection of the operator input device in the rod extension position.

[0004] Another aspect of the present disclosure relates to a construction machine comprising a pump, a pressure sensor, an operating cylinder, a downhole chamber pressure sensor, an operator input device, a main spool, a pilot valve, and a control device. The pressure sensor is configured to measure a pump pressure. The operating cylinder includes a rod operable to extend and retract. A downhole chamber of the operating cylinder is configured to be supplied with fluid from the pump during rod extension while fluid is removed from a rod-side chamber. The rod-side chamber of the operating cylinder is configured to be supplied with fluid from the pump during rod retraction while fluid is removed from the downhole chamber. The downhole chamber pressure sensor is configured to measure a downhole chamber pressure.The operator input device is movable between a neutral position, a rod extension position, and a rod retraction position. The operator input device includes a position sensor configured to measure the neutral position, the rod extension position, and the rod retraction position. The main spool is in fluid communication with the power cylinder and the pump. The pilot valve is in fluid communication with the main spool and the pump. The control device is communicatively coupled to the power cylinder and is programmed with an algorithm configured to output a signal to the pilot valve to control its output based on the sensed position of the operator input device.The algorithm is designed to confirm that the pump pressure exceeds the bore-side chamber pressure as a prerequisite for issuing a command that controls the movement of the pilot valve to extend the rod in response to the detection of the operator input device in the rod extension position.

[0005] The present disclosure further relates to a method for controlling a construction machine. The method includes a controller receiving a position signal from a position sensor that measures a neutral position, a rod extension position, and a rod retraction position of an operator input device. The controller receives a pump pressure of a pump from a pressure sensor. The controller receives a bore pressure from a bore pressure sensor on a bore side of a power cylinder, wherein the volume of the bore side of the power cylinder increases during rod extension and decreases during rod retraction. The controller receives a rod pressure from a rod pressure sensor on a rod side of the power cylinder, wherein the volume of the rod side of the power cylinder decreases during rod extension and increases during rod retraction.The controller analyzes the position signal, pump pressure, bore pressure, and rod pressure. The controller confirms that the pump pressure exceeds the bore pressure as a prerequisite for issuing a command that, in response to the operator input device detecting the rod extension position, controls the movement of the power cylinder to extend the rod. Short description of the drawings Fig. 1 shows a schematic representation of a hydraulic system and an associated boom cylinder of a construction machine. Fig. Figure 2 shows a flowchart detailing a control algorithm for the hydraulic system. Fig. 3 shows an example construction machine.

[0006] Before explaining embodiments of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. Other embodiments of the invention are also conceivable, and variously practiced or carried out. Detailed description

[0007] Fig. 1 is a schematic representation of a hydraulic system 10 for use in a construction machine 12 having a boom cylinder 14. The hydraulic system 10 may also be used with other working cylinders, such as a bucket cylinder and an arm cylinder. The boom cylinder 14 includes a rod 18 operable to extend and retract a boom of the construction machine 12. Examples of construction machines include skid steers, compact wheel loaders, mini excavators, and dump trucks. The boom cylinder 14 includes a bore-side chamber 22 and a rod-side chamber 26. The bore-side chamber 22 is disposed in the boom cylinder 14 such that the rod 18 extends outward as the fluid volume in the bore-side chamber 22 increases and the fluid volume in the rod-side chamber 26 decreases.The rod-side chamber 26 is arranged in the boom cylinder 14 around the rod 18 such that the rod 18 retracts into the boom cylinder 14 as the fluid volume in the rod-side chamber 26 increases and the fluid volume in the bore-side chamber 22 decreases. The fluid supplied to the bore-side chamber 22 and the rod-side chamber 26 is supplied through a main control valve 106 (e.g., a main spool) controlled by a control device 30. The control device 30 includes a control system 100 for a load-holding function of the load during the extension and retraction of the rod 18 of the boom cylinder 14 (Fig. Fig. 2). In contrast, solutions for holding the load during rod 18 extension and retraction utilize additional valves. U.S. Patent No. 10,590,962 describes the use of a pressure-compensating valve and a counterweight valve for load holding. U.S. Patent No. 5,579,642 describes the use of a post-compensated control valve for load holding. The hydraulic system 10 is capable of holding the load without additional valves through the integration of the control system 100. The control system 100 is discussed in more detail below.

[0008] The control device 30 may include one or more electronic processors and one or more memory devices. The control device 30 may be communicatively coupled to one or more sensors or other inputs as described herein. The electronic processor may be implemented as a programmable microprocessor, an application-specific integrated circuit (ASIC), one or more field-programmable gate arrays (FPGAs), a group of processing components, or other suitable electronic processing components. The memory device (e.g., a non-transitory, computer-readable medium) includes one or more devices (e.g., RAM, ROM, flash memory, hard disk storage, etc.) for storing data and / or computer code to perform or enable the various processes, methods, layers, and / or modules described herein.The storage device may include database components, object code components, script components, or other types of code and information to support the various activities and information structures described in the present application. By way of example, the storage device is communicatively coupled to the electronic processor and may include computer code for performing one or more processes described herein. The control device 30 may further include an input / output ("I / O") module. The I / O module may be configured to connect directly to one or more devices, such as a power supply, sensors, displays, etc. In one embodiment, the I / O module may utilize general-purpose I / O (GPIO) ports, analog inputs / outputs, digital inputs / outputs, etc. As described further below, the control device 30 may be programmed with an algorithm.

[0009] The algorithm of the control device 30 is designed to interpret and analyze a plurality of signals. The plurality of signals includes a bore-side pressure P A , a rod-side pressure P B , a pump pressure P P and a position signal cmd in . The bore-side pressure P A is measured by a bore-side pressure sensor 50, and the rod-side pressure P B is measured by a rod-side pressure sensor 54. The pump pressure P P is measured by a pressure sensor 58. The bore-side pressure sensor 50, the rod-side pressure sensor 54, and the pressure sensor 58 are pressure transducers. The pressure sensor 58 is connected to a pump line 62, which is connected to a pump 63. The position signal cmd inis measured by a position sensor 66 and is dependent upon the actuation of an operator input device 70 (ie a joystick) to a neutral position (in Fig. 1), a rod extension position 74 and a rod retraction position 78. The control device 30 is in data communication with each of the sensors 50, 54, 58, 66 so that the parameters measured by them can be transmitted periodically or continuously to the control device 30. The algorithm of the control device 30 analyzes the bore-side pressure P A , the rod-side pressure P B , the pump pressure P P and the position signal cmd inand determines whether to send a signal 82 to a first pilot valve 86 (in response to the rod extension position 74 of the operator input device 70) or a signal 90 to a second pilot valve 94 (in response to the rod retraction position 78 of the operator input device 70). Depending on the monitored conditions, the algorithm may instead ignore the rod extension or retraction command from the operator input device 70 and default to holding the load. Further details of a control system 100 of the algorithm of the control device 30 are discussed below ( Fig. 2).

[0010] Pump 63 is a variable displacement pump (e.g., an axial piston pump) that can change the displacement setting (e.g., via the swashplate angle) and is driven by a drive source 64. Drive source 64 can be an internal combustion engine or an electric motor to drive pump 63. Furthermore, pump 63 is variable for positive and negative displacement (i.e., reversible flow direction from a flow-generating "pumping" mode to a flow-receiving "motor" mode) and is referred to as a swashplate pump because it can switch between positive and negative during operation. Pump 63 may also be referred to as a variable displacement swashplate pump. In some designs, pump 63 may be a Bosch Rexroth A10VO with eOC control (also called EC4), although other pumps may be suitable. Pump 63 is fluidly connected to pump line 62 and supplies the pump pressure P PThe pilot valves 86, 94 are each capable of individually transitioning from an inactive state to an activated state in response to signals 82, 90. In the activated state, the pilot valves 86 and 94 receive signals 82 and 90, respectively, to enable fluid communication between a control pressure line 104 and the main control spool 106. The control pressure line 104 is maintained at a pressure between 25-30 bar by the pump 63 and causes the actuation of the main control spool 106.

[0011] When activated, the pilot valve 86 serves to extend the rod and enables the transfer of pressurized fluid from the control pressure line 104 into a line 107 to a first end 110 of the main spool 106. The pressurized fluid supplied through the line 107 actuates the main spool 106 against a biasing force provided by a spring 114 and brings the main spool 106 into a rod-extended position. The rod-extended position of the main spool 106 enables fluid communication between a first working port A, which is in fluid communication with the bore-side chamber 22 via the bore line 116, and the pump line 62. The pump line 62 supplies the bore line 116 and thus the bore-side chamber 22 with pressurized fluid to increase the fluid volume in the bore-side chamber 22 and extend the rod 18.The rod extension position of the main spool 106 provides fluid communication between a second working port B, which is in fluid communication with the rod-side chamber 26 via line 120, and the tank line 112. The tank line 112 is at atmospheric pressure, and when the rod is extended, fluid is directed from the rod-side chamber 26 into the tank line 112. Since the first pilot valve 86 is in the active state, the second pilot valve 94 must be in the inactive state to enable actuation of the main spool 106 to the rod extension position. The second pilot valve 94 provides fluid communication between a supply line 108, which is in fluid communication with the tank line 112, and a second end 118 of the main spool 106 via line 121.This allows the fluid to disperse at the second end 118 of the main spool 106 as the main spool 106 moves toward the rod extension position.

[0012] The second pilot valve 94, in the active state, serves to retract the rod and operates similarly to the first pilot valve 86 in its active state. Instead of the pressure fluid being directed from the control pressure line 104 to the first end 110 of the main spool 106, the pressure fluid is directed through the second pilot valve 94 via line 121 to the second end 118 of the main spool 106 to move the main spool 106 into a rod retraction position against the bias of a spring 122. The rod retraction position of the main spool 106 enables fluid communication between the second working port B and the pump line 62. The pump line 62 supplies the rod-side chamber 26 with pressure fluid via line 120 to increase the fluid volume in the rod-side chamber 26 and retract the rod 18.The rod retraction position of the main spool 106 enables fluid communication between the first working port A and the tank line 112 via the bore line 116. The bore-side chamber 22, as the fluid volume in the rod-side chamber 26 increases, directs fluid to the tank line 112 to enable extension of the rod 18. Because the pilot valve 94 is in the active state, the pilot valve 86 must be in the inactive state to enable actuation of the main spool 106 to the rod retraction position. The pilot valve 86 enables fluid communication between the supply line 108 and the first end 110 of the main spool 106 via line 107. This allows the fluid to spread at the first end 110 of the main spool 106 as the main spool 106 moves toward the rod retraction position.

[0013] In addition to the two states described above, the two pilot valves 86, 94 can be inactive simultaneously when the rod 18 is neither extended nor retracted. In the inactive state, the two pilot valves 86, 94 supply the main spool 106 with fluid at atmospheric pressure from the supply line 108. Since no pressure is present, the main spool 106 is biased by the springs 114, 122 into a neutral state in which both the first working port A and the second working port B with the main spool 106 are blocked from fluid communication with the pump line 62 and the tank line 112.

[0014] The hydraulic system 10 further includes a load sensing line 123, a shuttle valve 124, a bore-side pressure relief valve 126, and a rod-side pressure relief valve 130. The load sensing line 123 and the shuttle valve 124 are provided when the pump 63 is a hydromechanical load sensing pump. The bore-side pressure relief valve 126 is arranged between the bore line 116 and the tank line 112. The bore-side pressure relief valve 126 enables fluid communication between the bore-side chamber 22 and the tank line 112 when a bore-side pressure P Aexceeds a pressure threshold. The pressure threshold for the bore-side chamber is approximately 280 bar. In other designs, the pressure threshold may be less or more than 280 bar. The rod-side pressure relief valve 130 is arranged between the line 120 and the tank line 112 and provides pressure relief when the rod-side pressure P B exceeds 320 bar. In other designs, the pressure threshold for pressure relief valves 126 and 130 may be less or more than 320 bar.

[0015] Fig. Figure 2 shows the logic of the control system 100 used to control the fluid volume in the bore-side chamber 22 and the rod-side chamber 26 and thus the movement of the rod 18. The control system 100 begins in block 140 by turning on the construction machine 12. In block 144, the algorithm of the control device 30 receives the input signal cmd infrom the position sensor 66, the pump pressure P P , the bore-side pressure P A , and the rod-side pressure P B . In block 148, the algorithm detects whether the position of the operator input device 70 is in the neutral position ( Fig. 1). The algorithm continues with block 152 during the detection of the neutral position and executes the hold function by sending the output cmd out the control device for cylinder 18 is equal to the input signal cmd in sets (and cmd out = cmd in=0). In other words, none of the pilot valves 86, 94 are activated, and the main spool 106 remains in the neutral position. The algorithm is restarted in block 144, and the main spool 106 is held in the neutral position during the hold function (i.e., the pilot valves 86 and 94 do not receive an active state signal). As previously described, the algorithm proceeds from block 144 to block 148 to determine whether the operator input device 70 is in the neutral position ( Fig. 1).

[0016] If the operator input device 70 is not in the neutral position, the algorithm proceeds from block 148 to block 156 ( Fig. 1). The algorithm detects whether the position of the operator input device 70 is in the rod extension position 74 (ie cmd in> 0). If the operator input device 70 is in the rod extension position 74, the algorithm proceeds to block 160. In block 160, the algorithm checks whether the pump pressure P P greater than or equal to the sum of the bore-side pressure P A and a given tolerance amount is P mar (ie P P ≥ P A + P mar ). This can be generalized to the algorithm confirming that the pump pressure P P the bore-side pressure exceeds P A (since the specified tolerance amount P mar can be any positive value). In some conceivable designs, the specified tolerance amount P mar in the range of 20-30 bar. For other designs, the specified tolerance value P mar less than or more than 20-30 bar. The specified tolerance value P maris used to compensate for pressure losses across the main control spool 106, the lines, and other components of the hydraulic system 10. It therefore depends entirely on the design of the machine and can vary from machine to machine. The decision in block 160 is the prerequisite for the control device 30 to output cmd in block 164. out equal to entering cmd in In the illustrated design, this leads to the actuation of the first pilot valve 86 (signal 82, Fig. 1) to move the main control spool 106 and cause the rod to extend, since the operator input device 70 is in the rod extension position 74. The predetermined tolerance amount P maris integrated into the algorithm to ensure that there is no backflow in the pump line 62 to the pump 63 when the main spool 106 issues the rod extension command. As described above, load holding has previously been achieved by using additional valves to ensure that the pump pressure P P is set to the desired pressure before the rod is extended. The hydraulic system 10, in addition to the control system 100, achieves load holding by monitoring the position signal cmd in , the pump pressure P P , the bore-side pressure P A and the rod-side pressure P B and controlling the movement of the main spool 106 to extend the rod. The algorithm proceeds from block 160 to block 152 when the pump pressure P P less than the sum of the bore-side pressure P A and the specified tolerance amount P maris (ie the pump pressure P P does not exceed the bore-side pressure P A ) and continues with block 144 as described above. The algorithm can trigger an alarm to inform the user that the pump pressure P P less than the sum of the bore-side pressure P A and the specified tolerance amount P mar is when it transitions from block 160 to block 152, as the operator anticipates the rod to extend. The warning can be audible, visual, or physical (i.e., vibration) to inform the user of the load-holding function. The algorithm continuously monitors whether the pump pressure P P greater than or equal to the sum of the bore-side pressure P A and the specified tolerance amount P mar is.

[0017] The algorithm proceeds from block 156 to block 168 if the operator input device 70 is not in the rod extension position 74 (ie, cmd in > 0 is not fulfilled, or in other words cmd in < 0 and the operator input device 70 is in the rod retraction position 78). In block 168, the algorithm determines whether the pump pressure P P greater than or equal to a sum of the rod-side pressure P B and the specified tolerance amount P mar is (ie P P ≥ P B + P mar ). This can be generalized by having the algorithm confirm that the pump pressure P P the rod-side pressure P B The decision in block 168 is the prerequisite for the control device 30 to output cmd in block 164 out equal to entering cmd inIn the illustrated design, this leads to the actuation of the second pilot valve 94 (signal 90, Fig. 1) to move the main control spool 106 and cause the rod to retract, since the operator input device 70 is in the rod retraction position 78. The specified tolerance amount P mar is integrated into the algorithm to ensure that there is no backflow in the pump line 62 to the pump 63 when the main spool 106 issues the rod retraction command. As described above, load holding has previously been achieved by using additional valves to ensure that the pump pressure P P before the rod is retracted, the desired pressure is reached. If the pump pressure P P less than the sum of the rod-side pressure P B and the specified tolerance amount P marthe algorithm proceeds to block 152 and then continues to block 144 as described above. The algorithm may trigger an alarm to inform the user that the pump pressure P P less than the sum of the rod-side pressure P B and the specified tolerance amount P mar when moving from block 168 to block 152, as the operator anticipates the rod to extend. The algorithm constantly monitors whether the pump pressure P P greater than the rod-side pressure P B in addition to the specified tolerance amount P mar is.

[0018] Although the invention has been described in detail with reference to certain preferred embodiments, there are variations and modifications within the scope and spirit of one or more independent aspects of the invention as described. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 10,590,962

[0007] US 5,579,642

[0007]

Claims

[1] Construction machine, comprising: a pump; a pressure sensor configured to measure a pump pressure; a working cylinder with a rod that can be extended and retracted, wherein a bore-side chamber of the working cylinder is designed to to be supplied with fluid from the pump during rod extension while fluid is removed from a rod-side chamber, wherein the rod-side chamber of the working cylinder is adapted to be supplied with fluid from the pump during rod retraction while fluid is removed from the bore-side chamber; a bore-side chamber pressure sensor configured to measure a bore-side chamber pressure; an operator input device movable between a neutral position, a rod extension position and a rod retraction position, wherein the operator input device includes a position sensor configured to detect the neutral position, the rod extension position, and the rod retraction position; and a control device communicatively coupled to the working cylinder and programmed with an algorithm designed to control the movement of the working cylinder based on the detected position of the operator input device, wherein the algorithm is configured to confirm that the pump pressure exceeds the bore-side chamber pressure as a prerequisite for issuing a command that controls movement of the power cylinder to extend the rod in response to detecting the operator input device in the rod extension position. [2] The construction machine of claim 1, further comprising a rod-side chamber pressure sensor configured to measure a rod-side chamber pressure, wherein the algorithm is configured to confirm that the pump pressure exceeds the rod-side chamber pressure as a condition for issuing a command that controls movement of the power cylinder to retract the rod in response to detecting the operator input device in the rod retraction position. [3] The construction machine of claim 2, wherein the algorithm is configured to confirm that the pump pressure exceeds the rod-side chamber pressure by at least a predetermined tolerance amount as a prerequisite for setting the command that controls the movement of the power cylinder to retract the rod in response to detecting the operator input device in the rod retraction position. [4] The construction machine of claim 2, wherein the algorithm is configured to detect that the pump pressure does not exceed the rod-side chamber pressure and, in response to detecting the operator input device in the rod retraction position, perform a load holding function instead of setting the command controlling the movement of the power cylinder to retract the rod. [5] The construction machine of claim 1, wherein the algorithm is configured to confirm that the pump pressure exceeds the bore-side chamber pressure by at least a predetermined tolerance amount as a prerequisite for setting the command that controls movement of the power cylinder to extend the rod in response to detecting the operator input device in the rod extension position. [6] Construction machine according to claim 5, wherein the predetermined tolerance amount is designed to correspond to a pressure drop between the pump and the working cylinder. [7] The construction machine of claim 1, wherein the algorithm is configured to detect that the pump pressure does not exceed the bore-side chamber pressure and, in response to detecting the operator input device in the rod extension position, performs a load holding function instead of setting the command controlling the movement of the power cylinder to extend the rod. [8] Construction machine according to claim 1, further comprising: a main control spool connected to the working cylinder and the pump via a fluid line; and a pilot valve in fluid communication with the main spool and the pump, the pilot valve being designed to direct fluid to the main spool, which in turn directs fluid from the pump to the working cylinder, wherein the algorithm is configured to output a signal to the pilot valve in response to the operator input device in the rod extension position. [9] Construction machine according to claim 8, further comprising: a second pilot valve in fluid communication with the main spool and the pump, the second pilot valve being adapted to direct fluid to the main spool, which in turn directs fluid from the pump to the working cylinder, wherein the algorithm is configured to output a signal to the second pilot valve in response to the operator input device in the rod retraction position. [10] Construction machine according to claim 8, wherein the pump and the main control spool are connected directly and without intermediate hydraulic components via a pump line. [11] Construction machine, comprising: a pump, a pressure sensor configured to measure a pump pressure; a working cylinder with a rod that can be extended and retracted, wherein a bore-side chamber of the working cylinder is designed to to be supplied with fluid from the pump when the rod is extended, while fluid is removed from a rod-side chamber, wherein the rod-side chamber of the working cylinder is designed to be supplied with fluid from the pump when the rod is retracted, while fluid is removed from the bore-side chamber, a bore-side chamber pressure sensor configured to measure a bore-side chamber pressure; an operator input device movable between a neutral position, a rod extension position and a rod retraction position, wherein the operator input device includes a position sensor configured to measure the neutral position, the rod extension position, and the rod retraction position; a main control spool in fluid communication with the working cylinder and the pump; a pilot valve in fluid communication with the main spool and the pump; and a control device communicatively coupled to the working cylinder and programmed with an algorithm configured to output a signal to the pilot valve to control an output thereof based on the sensed position of the operator input device, wherein the algorithm is configured to confirm that the pump pressure exceeds the bore-side chamber pressure as a prerequisite for issuing a command that controls movement of the pilot valve to extend the rod in response to detecting the operator input device in the rod extension position. [12] Construction machine according to claim 11, wherein the pump and the main control spool are connected directly and without intermediate hydraulic components via a pump line. [13] The construction machine of claim 12, wherein the main spool is configured to enable fluid communication between the bore-side chamber and the pump in response to receipt of the signal by the pilot valve. [14] Construction machine according to claim 12, further comprising: a rod-side chamber pressure sensor configured to measure a rod-side chamber pressure; and a second pilot valve, wherein the algorithm is configured to confirm that the pump pressure exceeds the rod-side chamber pressure as a prerequisite for issuing a command that controls movement of the second rod retraction pilot valve in response to detecting the operator input device in the rod retraction position. [15] The construction machine of claim 14, wherein the main spool is configured to enable fluid communication between the rod-side chamber and the pump in response to receipt of the signal by the second pilot valve. [16] A method for controlling a construction machine, the method comprising: Receiving, with a control device, a position signal from a position sensor having a neutral position, a rod extension position and measures a bar retraction position of an operator input; Receiving, with the control device, a pump pressure of a pump from a pressure sensor; Receiving, with the controller, a bore pressure from a bore pressure sensor on a bore side of a working cylinder, wherein the volume of the bore side of the working cylinder increases during rod extension and decreases during rod retraction. Receiving, with the controller, a rod pressure from a rod pressure sensor on a rod side of the power cylinder, wherein the volume of the rod side of the power cylinder decreases during rod extension and increases during rod retraction. Analyze, with the control device, the position signal, the pump pressure, the bore pressure and the rod pressure. Confirming with the control device, in response to identifying the operator input in the rod extension position, that the pump pressure exceeds the bore pressure as a prerequisite to issuing a command that controls the movement of the power cylinder to extend the rod. [17] The method of claim 16, further comprising identifying with the controller, in response to identifying the operator input in the rod extension position, that the pump pressure does not exceed the bore pressure, and responding with the controller by performing a load holding function instead of issuing a command that controls movement of the power cylinder to extend the rod. [18] The method of claim 16, further comprising confirming with the controller, in response to identifying the operator input in the rod retraction position, that the pump pressure exceeds the rod pressure as a condition for issuing a command controlling movement of the power cylinder to retract the rod. [19] The method of claim 18, further comprising identifying with the controller, in response to identifying the operator input in the rod retraction position, that the pump pressure does not exceed the rod pressure, and responding with the controller by performing a load holding function instead of issuing a command controlling movement of the power cylinder to retract the rod.

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