Abstract: Apparatus for automatically steering a farm crop vehicle between rows of corn by sensing the locations of the rows ahead of the vehicle. The apparatus senses the location of the plants as the crop vehicle approaches them. The data thus obtained are processed by an on-board microcontroller to determine the lateral location of the crop vehicle relative to the rows and provide a feedback signal. Another feedback signal is provided by integrating that lateral error data. In addition to the plant sensors, the harvester has a Doppler radar system on its left side that provides ground-velocity information for the left side, and a similar system on the right side. The radar outputs enable the microcontroller to measure the turning of the vehicle. This is used to produce yet another feedback signal that improves the automatic steering. This turning-feedback signal stabilizes the loop. The microcontroller provides steering commands for automatically tracking the rows.

Abstract: Apparatus for automatically steering a farm crop vehicle into rows of corn by sensing the locations of the rows ahead of the vehicle on both sides of the vehicle. The apparatus senses the plants of each row by means of contact sensors that touch the plants as the crop vehicle approaches them. The data thus obtained are processed by an on-board microcontroller to determine the lateral location of the crop vehicle relative to the rows. Also, the frequencies of encountering plants in laterally spaced-apart rows provided information regarding turning of the vehicle, i.e., incipient changes of lateral position. This is used to produce a further feedback signal that improves the automatic steering, especially where the rows are curved. Having the turning-feedback signal in the servo loop also permits higher loop gain without instability, which reduces tracking error even further.

Abstract: A pilot control valve (35) is provided for use in a load sensing system including a priority flow control valve (21). The pilot valve includes a flow orifice (47) through which passes flow from the priority outlet port (23) to the motor (13). The pilot valve includes a valve sleeve (73) and a relatively rotatable valve spool (75). This valving controls fluid communication between the load signal port (49) and the system reservoir and main flow path, upstream and downstream of the flow orifice. Movement of the valve spool from a minimum flow position to a maximum flow position progressively varies the load signal (51) from reservoir pressure to system pressure, thus causing the output of the priority valve (21) to progressively increase from a minimum flow to a maximum flow.

Abstract: A system is disclosed for controlling the flow of fluid from a pair of pumps (15,15') to a steering system (11) and a pair of auxiliary load circuits (13,13'). The steering system includes valving (43) defining a variable flow control orifice (45), and the steering system normally operates with a pressure differential X across the variable orifice, and provides load pressure signals (47,49,49',53,53') representative of demand for fluid by the steering system. Fluid flow from the pumps is controlled by a pair of priority flow control valves (21,21') including a pair of valve members (27,27') each of which is biased by a spring (29,29') toward a position permitting flow to the steering system. The spring (29) exerts a biasing force equivalent to the pressure differential X while the spring (29') exerts a biasing force equivalent to a pressure differential Y, which is less than X.

Abstract: A controller for fluid pressure operated devices such as vehicle power steering systems. The controller is of the type having a primary, rotatable valve member and a follow-up valve member and including a fluid meter having a metering member coupled to the follow-up valve member. The valving defines a central reference plane perpendicular to the axis of rotation of the valving and the various ports and passages defined by the primary and follow-up valve members are generally oppositely and equally disposed about the central reference plane. This valving symmetry reduces internal leakage and steering wheel precession. The controller includes a load signal circuit, including a pair of load sensing grooves oppositely and equally disposed about the central plane.

Abstract: A fluid controller is disclosed of the type including a primary valve member, and a follow-up valve member. The controller includes a load signal port and a load signal chamber. Fluid is communicated from the inlet port to the load signal chamber, and the valve members define a neutral orifice communicating between the load signal chamber and the return port when the valving is in neutral. The valving defines operating orifices communicating fluid from the load signal chamber to the main fluid path, downstream of the main flow control orifice, when the valving is shifted away from neutral. The operating orifices have a smaller orifice area when the valving approaches maximum deflection. The result is a substantially higher differential operating pressure, and a higher flow rate than would otherwise be possible at that particular valve deflection.

Abstract: A controller for fluid pressure operated devices such as power steering systems. The controller is of the type having a primary, rotatable valve member and a follow-up valve member and including a fluid meter having a metering member coupled to the follow-up valve member. The valving defines a central reference plane perpendicular to the axis of rotation of the valving, the primary valve member defining a pair of meter grooves oppositely and equally disposed about the plane. The follow-up valve defines pressure porting adjacent the plane and connected to the fluid inlet port.