Control systems for drive systems and work elements of power machines

Abstract

Systems and methods for power machine drive control are provided. The drive control system can include a foot input and a hand input in an operator station of a compact tractor that can each be configured to independently provide forward and reverse (or other) drive commands. In addition, a hydraulic control systems and methods for work element operations of a power machine are provided. Functions of an implement can be configured to operate based on inputs from a dual-axis joystick. The dual-axis control over an implement provides a first function (e.g., a lift function) to remain in a float configuration while allowing the operator to command a second function (e.g., a tilt function).

What is claimed is: 
     
         1 . A power machine comprising:
 a power source;   drive motors operably coupled to the power source and to tractive elements of the power machine to power drive operations of the power machine;   a first drive input device configured to provide a first control signal to selectively power operation of the drive motors for travel in a forward direction or a reverse direction; and   a second drive input device configured to provide a second control signal to selectively power operation of the drive motors for travel in the forward or the reverse direction;   wherein the first drive input device is independently movable relative to the second drive input device to provide the first control signal and the second drive input device is independently movable relative to the first drive input device to provide the second control signal.   
     
     
         2 . The power machine of  claim 1 , further comprising:
 a drive pump operably coupled to the power source and configured to power the drive motors to selectively drive the power machine in the forward direction or the reverse direction;   wherein the drive motors are hydraulically powered drive motors; and   wherein the first drive input device is configured to provide the first control signal to control the drive pump to selectively power operation of the drive motors for travel in the forward direction or the reverse direction; and   wherein the second drive input device is configured to provide the second control signal to control the drive pump to selectively power operation of the drive motors for travel in the forward or the reverse direction.   
     
     
         3 . The power machine of  claim 1 , wherein the first drive input device includes a single-axis joystick. 
     
     
         4 . The power machine of  claim 1 , wherein the second drive input device includes at least one foot pedal. 
     
     
         5 . The power machine of  claim 1 , wherein the first drive input device and the second drive input device are in hydraulic communication with a hydraulically operated control device arranged to provide pilot-operated control of displacement of a drive pump using hydraulic pressure within a drive control hydraulic circuit;
 wherein the drive control hydraulic circuit includes a first control path that includes a first shuttle valve between the hydraulically operated control device and a first outlet port of each of the first and second drive input devices, with first inlets of the first shuttle valve in hydraulic communication with the first outlet ports, and with a first outlet of the first shuttle valve in hydraulic communication with the hydraulically operated control device to provide a first pilot control signal to the hydraulically operated control device; and   wherein the drive control hydraulic circuit includes a second control path that includes a second shuttle valve between the hydraulically operated control device and a second outlet port of each of the first and second drive input devices, with second inlets of the second shuttle valve in hydraulic communication with the second outlet ports, and with a second outlet of the second shuttle valve in hydraulic communication with the hydraulically operated control device to provide a second pilot control signal to the hydraulically operated control device opposed to the first pilot control signal.   
     
     
         6 . A hydraulic control circuit for a drive system of a power machine, the hydraulic control circuit comprising:
 a first drive input device in communication with a pilot pressure source and configured to receive a first operator input relative to a first degree of freedom and to selectively provide, based on the first operator input, a first pilot signal along first control path or along a second control path to command, respectively, operation of a drive motor of the drive system in a forward direction or a reverse direction;   a second drive input device in communication with a pilot pressure source and configured to receive a second operator input relative to a second degree of freedom and to selectively provide, based on the second operator input, a second pilot signal along the first control path or along the second control path to command, respectively, operation of the drive motor of the drive system in the forward direction or the reverse direction;   a pilot-operated actuator configured to control a displacement of the drive motor based on pilot signals from the first and second control paths;   a first shuttle valve arranged along the first control path between the pilot-operated actuator and the first and second drive input devices; and   a second shuttle valve arranged along the second control path between the pilot-operated actuator and the first and second drive input devices.   
     
     
         7 . The hydraulic control circuit of  claim 6 , wherein the first drive input device includes a joystick and the second drive input device includes a pedal. 
     
     
         8 . A power machine comprising:
 a power source;   a work element configured to be powered by the power source for work operations;   an implement interface configured to removably, operably couple an implement to the power machine;   at least one power coupler configured to transmit power from the power machine to the implement when the implement is removably, operably coupled to the implement interface; and   a dual-axis joystick;   wherein movement of the dual-axis joystick along a first axis actuates a first actuator configured for a first work function;   wherein movement of the dual-axis joystick along a second axis actuates a second actuator of the implement that is powered via the at least one power coupler for a second work function of the implement;   wherein the dual-axis joystick being positioned at a first threshold position along the first axis places the first actuator in a float configuration for the first work function; and   wherein the dual-axis joystick being positioned at a second threshold position along the second axis places the second actuator in a float configuration for the second work function.   
     
     
         9 . The power machine of  claim 8 , further comprising:
 an auxiliary pump operably coupled to the power source and configured to pressurize a work actuator circuit that includes the first actuator;   wherein the at least one power coupler is configured to place the implement in fluid communication with the work actuator circuit to transmit hydraulic power from the power machine to the implement;   wherein the dual-axis joystick is operably coupled to a first hydraulic control spool and a second hydraulic control spool;   wherein movement of the dual-axis joystick along the first axis adjusts a position of the first hydraulic control spool to selectively provide pressurized fluid from the auxiliary pump to actuate the first actuator;   wherein movement of the dual-axis joystick along the second axis adjusts a position of the second hydraulic control spool to selectively provide pressurized fluid from the auxiliary pump to the at least one power coupler for actuation of the second actuator;   wherein, when the dual-axis joystick is positioned at the first threshold position along the first axis, the first hydraulic control spool is positioned to place the first actuator in the float configuration for the first work function; and   wherein, when the dual-axis joystick is positioned at the second threshold position along the second axis, the second hydraulic control spool is positioned to place the second actuator in the float configuration for the second work function.   
     
     
         10 . The power machine of  claim 9 , further comprising:
 a switch in communication with a control system of the power machine, the switch arranged to be actuated by movement of the dual-axis joystick to a third threshold position along the first axis;   wherein, upon actuation of the switch, the control system is configured to implement a float assist mode in which the auxiliary pump provides pressurized flow in the work actuator circuit to resist but not stop movement of the first actuator under external loads.   
     
     
         11 . The power machine of  claim 10 , wherein the first threshold position is different from the second threshold position. 
     
     
         12 . The power machine of  claim 10 , further comprising:
 a first solenoid valve arranged on a first side of the first actuator and a second solenoid valve on a second side of the first actuator;   wherein actuation of the switch commands control of the first and second solenoid valves to implement the float assist mode; and   wherein the first and second solenoid valves are configured to remove the first actuator from fluid communication with the first hydraulic control spool.   
     
     
         13 . The power machine of  claim 12 , wherein, when the switch is actuated, the first solenoid valve places the first side of the first actuator in fluid communication with an adjustable pressure relief valve configured to adjust a pressure delivered to the first side of the first actuator by the auxiliary pump. 
     
     
         14 . The power machine of  claim 8 , further comprising:
 a bracket coupled to the dual-axis joystick and configured to engage a switch to implement a float assist mode when the dual-axis joystick is positioned at a maximum end position along the first axis, across a range of positions along the second axis.   
     
     
         15 . The power machine of  claim 14 , wherein the bracket extends along the second axis such that the bracket maintains contact with the switch during movement of the dual-axis joystick along the second axis within the range of positions along the second axis. 
     
     
         16 . A power machine assembly comprising:
 the power machine according to  claim 8 ; and   the implement, operably coupled to the implement interface of the power machine and to the at least one power coupler.   
     
     
         17 . A power machine comprising:
 a power source;   a hydraulic pump operably coupled to the power source and configured to pressurize a work actuator circuit;   a work element configured to be powered by the hydraulic pump for work operations;   a dual-axis joystick; and   a switch in communication with a control system of the power machine;   wherein movement of the dual-axis joystick along a first axis selectively provides pressurized fluid from the hydraulic pump to actuate a first actuator configured for a first work function;   wherein movement of the dual-axis joystick along a second axis selectively provides pressurized fluid from the hydraulic pump to actuate a second actuator configured for a second work function;   wherein, when the dual-axis joystick is positioned at a first threshold position along the first axis, the dual-axis joystick actuates the switch to place the first actuator in a float configuration for the first work function; and   wherein, upon actuation of the switch, the control system is configured to implement a float assist mode in which the hydraulic pump provides pressurized flow in the work actuator circuit to resist but not stop movement of the first actuator under external loads.   
     
     
         18 . The power machine of  claim 17 , wherein the dual-axis joystick is operably coupled to a first hydraulic control spool and a second hydraulic control spool;
 wherein movement of the dual-axis joystick along the first axis adjusts a position of the first hydraulic control spool to selectively actuate the first actuator;   wherein movement of the dual-axis joystick along the second axis adjusts a position of the second hydraulic control spool to selectively actuate the second actuator; and   wherein, when the dual-axis joystick is positioned at the first threshold position along the first axis, the dual-axis joystick positions the first hydraulic control spool to place the first actuator in the float configuration.   
     
     
         19 . The power machine of  claim 17 , wherein the hydraulic pump is an auxiliary pump. 
     
     
         20 . A power machine comprising:
 an implement interface configured for operably coupling a removable implement to the power machine;   a work element;   a power source;   an auxiliary pump operably coupled to the power source and configured to pressurize a work actuator circuit, the work actuator circuit including:
 a first actuator arranged to be powered by the auxiliary pump to power work operations with the work element; and 
 at least one power coupler configured to selectively provide pressurized fluid to the removable implement when the removable implement is operably coupled to the at least one power coupler; and 
   a dual-axis joystick operably coupled to a first hydraulic control spool and a second hydraulic control spool;   wherein movement of the dual-axis joystick along a first axis adjusts a position of the first hydraulic control spool to selectively provide pressurized fluid from the auxiliary pump to actuate the first actuator;   wherein movement of the dual-axis joystick along a second axis adjusts a position of the second hydraulic control spool to selectively provide pressurized fluid from the auxiliary pump to the at least one power coupler for actuation of a second actuator arranged on the removable implement.