Excavating – Ditcher – Condition responsive
Reexamination Certificate
2003-01-14
2004-05-18
Pezzuto, Robert E. (Department: 3671)
Excavating
Ditcher
Condition responsive
C701S050000
Reexamination Certificate
active
06735889
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the calibration of a neutral position for hand or foot manual controls such as would be used in a work vehicle, such as, for example a mini excavator or skid steer loader. In particular, the present invention relates to an apparatus and method automatically correcting sensor output drift utilizing a “moving average” to correct for control and position sensor drift.
BACKGROUND OF THE INVENTION
Skid steer loaders are work vehicles that include four wheels rotatably mounted to a frame, an engine mounted on the frame and connected by a transmission to rotate at least two wheels, a cab compartment mounted on the frame that includes a seat for an operator, manual controls and a display panel disposed in the cab compartment, a boom arm assembly rotatably mounted on the frame and connected to a pair of hydraulic boom cylinders for moving the boom arm assembly, and an implement assembly connected to the boom arm assembly. Typically, one or more hydraulic cylinders are used to manipulate the implement assembly. The implement assembly may be, for example, a bucket assembly, wherein the implement is a bucket and a pair of hydraulic bucket cylinders is used to move the bucket assembly. Other types of work vehicles that are similar to skid steer loaders include tractors, bulldozers and mini-excavators.
To operate the hydraulic boom cylinders and the hydraulic bucket cylinders, an operator in the cab manipulates either hand or foot manual controls. The skid steer loader, or similar work vehicle, includes an electronic control circuit system that includes an onboard computer, microprocessor, or controller. For the purposes of this disclosure a computer, microprocessor, or controller are considered to be equivalent and interchangeable elements. The onboard computer operates solenoids or digital coils of electroliydraulic valves that activate the hydraulic boom and bucket cylinders.
To properly operate the hydraulic boom cylinders and the hydraulic implement cylinders, each manual control is associated with a control and position sensor that generates input signals and sends them to the controller. The input signals generated by each sensor correspond proportionately to a displacement of the particular manual control from a neutral position. Generally, the neutral position is memorized and stored in the memory storage unit that is either integral with, or connected to, the controller. The controller receives the control and position sensor input signals, compares the information provided by these sensors to the memorized neutral position data, then generates output control signals used to control the operation of electrohydraulic valves, such as spool valves or cartridge valves, Thus, the controlled operation of the electrohydraulic valves activates the hydraulic cylinders of the boom arm assembly and the implement assembly to effect movement of the boom arm assembly and the implement carried by the boom arm assembly. In this way, an operator directs the desired movement on the boom arm assembly and the implement by manipulating manual controls in the cab of the work vehicle.
One such work vehicle is the skid steer loaded disclosed in U.S. Pat. No. 5,924,516 to Sagaser et al., which is incorporated herein by reference in its entirety. Sagaser et al. discloses an electronic control system for a skid steer loader (“skidder”) that includes a controller receiving inputs from an interface controller, position sensors associated with a hand grip and foot pedal manual controls, and a feedback signal from a linear actuator. The controller generates outputs to the linear actuator, which in turn activates a hydraulic spool valve that activates a hydraulic cylinder such as is connected to effect movement of a boom arm assembly or an implement carried by the boom arm assembly.
The hand grip and foot pedal manual controls are biased to a neutral position. The controller is programmed so that, upon power-up, the controller determines whether the manual controls are in a neutral position (or within some predetermined range of the neutral position) or not based on the data provided by position sensors associated with each manual control. If the manual controls are not in the neutral position, or not within some predetermined range of the neutral position, the controller sends a signal to the interface controller instructing the interface controller to inhibit certain operations of the loader until the manual controls are placed in the neutral position for some predetermined time period. In this manner, the loader is provided with a safety feature that prevents sudden and accidental operation of either the boom arm assembly and/or the implement assembly in case the operator starts up the loader with the manual controls significantly displaced from the neutral position.
However, the prior art work vehicles have certain drawbacks. First, the position information provided by the manual control and position sensors is susceptible to drift over time. Specifically, control and position sensors are partially sensitive to environmental changes such as variations in temperature. This dependence of each sensor on environmental factors is referred to as “sensor drift.” Besides being partially temperature sensitive, the operational relationship between each control and position sensor and its associated manual control is partially sensitive to changes in the mechanical linkage between the manual controls and the sensors themselves. This dependence of the functioning of the sensor-manual control pair on the mechanical linkage between the sensor and the manual control is referred to, for the purposes of this disclosure, as “linkage drift.” The ever changing problem caused by the naturally occurring “sensor drift,” i.e., sensor signal fluctuation secondary to temperature changes, and some degree of “linkage drift,” i.e., eventual changes over time in the mechanical linkage between the manual controls and the sensors themselves, is that the physical neutral position of the manual controls may not correspond precisely to the memorized neutral position. This drift in the physical neutral position from the memorized neutral position is referred to as “neutral drift” and is a function of, at least, sensor drift and linkage drift.
The prior art work vehicle has the disadvantage that the memorized neutral position stored in a memory storage device is fixed and there is no algorithm providing compensation for the neutral drift. The practical result of neutral drift is an eventual improper matching between the physical neutral position of the manual controls and the memorized neutral position stored in the memory storage device, which results in improper movement control of the boom arm assembly and/or the implement assembly when the physical neutral position is misperceived by the controller. Consequently, unexpected operation of the boom arm assembly and the implement assembly result as the manual controls are no longer precisely matched to movement in the boom arm assembly and implement assembly. In other words, the boom arm assembly and the implement can not be positioned as desired because the controller of the skid steer loader, or similar type of work vehicle, does not recognize when the manual controls are in the neutral position; therefore, the controller can not properly generate output control signals proportionate to the amount of displacement of the manual controls from the physical neutral position. Furthermore, when the controller can not properly recognize when the manual controls are in the neutral position, it becomes a more difficult task to get the controller to enable the operation of the boom arm assembly and the implement assembly instead of operating to inhibit operations of these assemblies.
From the previous discussion, it is clear that there is a need to correct for neutral drift. However, the particular amount of neutral drift between any one control and position sensor and its associated manual control is a physical limitation of the sensor and its m
Berger John G.
Haupt John R.
New Holland North America Inc.
Pezzuto Robert E.
Stader John William
Webb Collin A.
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