Patent GB-885108-A (GB)
Title: Improved road vehicle steering system
IPC: B62D6/00
Filed: 1959-12-16
Abstract: 885,108. Automatic steering control systems. GENERAL MOTORS CORPORATION. Dec. 16, 1959 [Jan. 8, 1959], No. 42768/59. Class 38 (4). [Also in Group XXXI] In a road-vehicle steering system, the dirigible wheels are controlled by a servo-mechanism from the manual steering wheel through an electronic control system which is responsive to the steering wheel and to one or more operating conditions such as vehicle yaw, body roll or lateral acceleration. The road wheels 12 are steered through a linkage 16, 18 from a sector 22 engaging a rack 26 formed upon a nut which is reciprocated by rotation of a worm 24 formed upon a shaft 30 which may be engaged through a clutch 32 to the shaft 28 of a steering wheel 14 for direct steering, or may be reciprocated by an hydraulic ram 42 actuated in response to an electronic signal dependent upon the steering-wheel rotation. Additional signals may be fed to the circuit to provide " feel " and from a computer system in response to one or more of the above mentioned variables. In the control circuit, the first and second input leads 46 and 48 connect with two-position switches 48 and 50 respectively, one pole 52 of switch 46 is idle while the other is connected to a variable-gain device 58, which may be manually adjustable to any desired level and in which the output signal varies in response to the reciprocal of the vehicle speed. One pole 64 of switch 50 connects with a variable-gain device 66 that gives a signal dependent upon the reciprocal of the vehicle speed, the output of which is connected to a switch 62 through a manually adjustable gain device 68 and which may be shorted out by direct connection between pole 64 of the switch 50 and the device 68. The switch 62 feeds into a conventional summation network 70, which also receives a feedback signal from a pick-up 80 indicating the extent of steering movement. Other signals are received at 62, at 82 from a computer section 38, and at 86 dependent upon variation in the trim of the vehicle. The valve 87 of the hydraulic system is controlled from the summation apparatus 70 through an amplifier 85. A torque reaction to the steering shaft 28-to give " feel "-is provided by a servomotor 88 controlled by a valve 202. The output of a multi-turn potentiometer 90, which is connected to the drive shaft of the servomotor 88, is fed to an adjustable gain device 92, switch 94, variable gain device 96 and position input 44 of the steering servo system. A strain gauge 98 on the column 28 is connected through a switch 100 to the torque input 48 and to an adjustable gain device 106. An electric generator 108 may be geared to the steering column to produce a signal dependent on the rate of turn of the steering wheel and feeds to an adjustable gain device 110 and to a variable gain device 112, the outputs of which are combined in a circuit 114 and supplied to a switch 116. A strain gauge 122 in the steering gear may be connected to the device 144 in the computer system feeding to the network 126 which may receive an input signal through either a variable gain device 96 or an adjustable gain device 92. The network 126 also receives signals from the gain device 106, the summing circuit 114, the switches 127, 128 and possibly from an input 146 dependent upon the trim of the vehicle. The output of 126 is the algebraic sum of the input signals and is fed through 148 to an amplifier 150 and to the valve 89 controlling the motor 88, tending to turn the steering shaft 28. Instruments such as a roll rate gyroscope, a roll indicator, a yaw rate gyroscope which may also produce a signal dependent upon yaw accelerator, an accelerometer responsive to the lateral acceleration of the vehicle and a tachometer producing a signal dependent upon the vehicle speed may be included in a box 152 and their outputs fed to a computer 158 having variable gain controls 160, 162 and 164 for controlling the strength of the stability signals. The output 166 of the computer 158 may be a group of or a single conductor connected to the switch 82 of the summation network 70. A second group of outputs 170 from the instruments 152 is connected to a computer 174 having gain controls 176, 178, 180 for individually controlling the strength of the stability signals. The strength of the signals in computer 174 may be varied relatively to that in computer 158. The output of computer 174 is connected to network 126. The speed signal is applied to a multiplying circuit 186 producing signals at 188, 190, 192 which are functions of the speed, its reciprocal and its square connected to variable gain devices 58, 66, 112 and 96. Engagement of the clutch 32 for direct manual steering opens valves 200 and 202 for by-passing the motors 40, 88. In one form of operation, a variable stability switch control 204 is opened and the " feel " servo switch 208 closed. The network 70 does not receive signals from computer 158. The switches 94, 116 and 128 open and the feel summing network receives no signals from 174 or from potentiometer 90 and generator 108, but switch 142 is closed and the summation network 126 receives a signal from the strain gauge 122 dependent upon the force on the dirigible wheels 12. Switch 206 closes switch 46 so that potentiometer 90 feeds a signal to network 70. A position signal is fed back to pick up 80 in network 126 and the wheels 12 are turned to an extent dependent upon the difference between the steering wheel position signal and the dirigible wheel signal, the steering ratio being a function of the variable gain device 58 dependent upon the reciprocal of the vehicle speed. Other steering operations with both switches 204 and 206 being closed and switch 204 closed and switch 206 open are described. Specification 814,496 is referred to.