GB1380029A - Attitude control system apparatus - Google Patents

Abstract

1380029 Graders SYSTRON-DONNER CORP 22 March 1973 [30 March 1972] 13873/ 73 Heading E1F [Also in Division G3] In a system for maintaining the angle of tilt of part of a machine relative to the horizontal despite movements of the machine as a whole, undesired motion of the said part is detected by a linear accelerometer and by a device responsive to angular movement, the signals from which are combined to control correcting means. As shown, the system controls the blade on an earth scraper but it may also be used for stabilising a passenger compartment suspended in a rail vehicle (Fig. 10, not shown). In the earth scraper application the system controls a hydraulic actuator 47 at one end of the blade, while a similar actuator 46 at the opposite end is controlled by the difference between a reference potentiometer 63 and a potentiometer 67 actuated 'by a feeler in contact with a guide wire; thus the height of one end of the blade relative to the wire is kept constant, and the invention keeps its tilt constant. The desired tilt is entered on potentiometer 87 for comparison with the output of combining circuit 97 to control cylinder 47. As shown, circuit 97 double integrates the output of an angular accelerometer 94 mounted on the blade. The output of a linear accelerometer 93 also mounted on the blade, with its effective direction perpendicular to the tilt axis is compared with the output of 97 at 139 and the difference is fed to 97 via a "bias error corrector circuit" 95. This cancels any drift caused by the double integration of any zero error in accelerometer 94. An RC filter 101, 102 allows short time constant signals during actual movement. A phase lead network 96 ensures stability. The signal from 93 will contain an unwanted component due to accelerations of the machine in the direction of its travel; this is cancelled by the arrangement 82 in which an engine driven tachometer signal 125 is differentiated at 126, or a second linear accelerometer 145 is provided, and the result is multiplied by the sine of the angle the blade makes with the direction of travel. The cosine of this angle is also supplied as a feedback to the circuit 97, to adjust the integrated output of 94 for this angle. (The blade must be tilted by a different amount to achieve a desired resultant tilt if the blade is not perpendicular to the travel direction). The circuit 97 also has a low pass filtering action, to remove effects of machine oscillation due to flexibility of its tyres, &c 88 is an indicator. In a simpler system (Fig. 12, not shown) the angular accelerometer is replaced by an angular rate sensor and only single integration is required.