Abstract: A controller for controlling the slope of a screed supported by support arms wherein the screed is moved over a distance includes a first slope sensor which develops a first sensor signal representing the slope of the screed, a second slope sensor which develops a second sensor signal representing the slope of the support arms and a first summer which sums the first sensor signal and command signal indicative of a particular screed slope to develop a first error signal. An integrator integrates the error signal over distance to develop an integrated first error signal. A second summer sums the integrated first error signal with the second sensor signal to develop a second error signal which is utilized to control actuators which adjust the slope of the support arms.

Abstract: Machines having a boom or arm pivotally disposed thereon wherein the length of the boom or arm and the angle thereof with respect to a reference plane are adjustable by means of actuators are well known. However, it is extremely difficult, if not impossible, to simultaneously control the actuators in a coordinated fashion to move the end of the boom or arm in a straight line path. In order to overcome this problem, a boom control system for a boom according to the present invention controls the actuators in either of two modes of operation, the first mode of operation comprising independent control over each actuator to afford polar coordinate operation and the second mode of operation comprising synchronized control over the actuators so that the end of the member may be moved in a straight line. Means are provided for manually selecting one of the two modes of operation. Means may be provided for calculating the amount of remaining horizontal throw of the boom or arm when a command to move same is issued.

Abstract: Machines having a boom or arm pivotally disposed thereon wherein the length of the boom or arm and the angle thereof with respect to a reference plane are adjustable by means of actuators are well known. However, it is extremely difficult, if not impossible, to simultaneously control the actuators in a coordinated fashion to move the end of the boom or arm in a straight line path. In order to overcome this problem, a boom control system for a boom according to the present invention controls the actuators in either of two modes of operation, the first mode of operation comprising independent control over each actuator to afford polar coordinate operation and the second mode of operation comprising synchronized control over the actuators so that the end of the member may be moved in a straight line. Means are provided for manually selecting one of the two modes of operation. Means may be provided for calculating the amount of remaining horizontal throw of the boom or arm when a command to move same is issued.

Abstract: Machines having a boom or arm pivotally disposed thereon wherein the length of the boom or arm and the angle thereof with respect to a reference plane are adjustable by means of actuators are well known. However, it is extremely difficult, if not impossible, to simultaneously control the actuators in a coordinated fashion to move the end of the boom or arm in a straight line path. In order to overcome this problem, a boom control system for a boom according to the present invention controls the actuators in either of two modes of operation, the first mode of operation comprising independent control over each actuator to afford polar coordinate operation and the second mode of operation comprising synchronized control over the actuators so that the end of the member may be moved in a straight line. Means are provided for manually selecting one of the two modes of operation. Means may be provided for calculating the amount of remaining horizontal throw of the boom or arm when a command to move same is issued.

Abstract: Actuators typically include one or more coils which are driven by a current source to effect positioning of a movable member. However, faults can occur wherein a conductor connecting the coil to the current source is open circuited or short circuited to ground. This can lead to a loss of control over the actuator, in turn creating a potentially dangerous condition. In order to overcome this problem, an actuator driver circuit according to the present invention includes a first current source for generating a first current at an output terminal thereof, a second current source for generating a second current at an output terminal thereof and first and second actuator coils connected in parallel between the output terminals of the first and second current sources. The current sources are controlled so that at least one of the current sources is capable of generating current for the coils even in the event of an open or short circuit fault condition.