Mobile elevated work platform vehicles with novel steering system and related methods

A mobile elevated work platform vehicle comprising:

• a. a vehicle chassis having a central compartment, a first lateral compartment, and a second lateral compartment;
• b. a first independently steerable wheel mounted to rotate about a first geometrically fixed steering axis relative to said vehicle chassis;
• c. a first linear steering actuator in mechanical communication with said first independently steerable wheel and nested within said first lateral compartment;
• d. a second independently steerable wheel mounted to rotate about a second geometrically fixed steering axis relative to said vehicle chassis;
• e. a second linear steering actuator in mechanical communication with said second independently steerable wheel and nested within said second lateral compartment, wherein there is no mechanical linkage between said first independently steerable wheel and said second independently steerable wheel;
• and
• f. a controller having a processor for processing data, a memory, and a data storage device for storing data, wherein the data storage device has instructions, executable by the processor, to perform the machine-implemented steps of:
• i. receiving a first signal representative of a first toe angle based on the position of said first linear steering actuator of said first independently steerable wheel,
• ii. calculating a target toe angle for said second independently steerable wheel based on a predetermined steering geometry, said position of said first linear steering actuator, and at least one wheelbase geometric dimension of said vehicle,
• iii. receiving a second signal representative of a second toe angle of said second independently steerable wheel;
• iv. calculating an angular difference between said target toe angle and said second toe angle to create a steering command, and sending said steering command from said controller to said second linear steering actuator for said second independently steerable wheel to turn said second independently steerable wheel to the target toe angle.

A method for determining steering geometry of a vehicle of a type having first and second independently steerable wheels, wherein each independently steerable wheel is mounted to rotate about a geometrically fixed steering axis relative to a vehicle chassis, and a steering system comprises a controller, wheel angle sensor devices for generating toe angle signals representative of toe angles of the steerable wheels, the method comprising the machine-implemented steps of:

• i. receiving a first signal representative of a first toe angle of a first independently steerable wheel, wherein said first toe angle is determined relative to a predetermined reference point corresponding to a zero position of a first linear steering actuator associated with said first independently steerable wheel;
• ii. calculating a target toe angle for a second independently steerable wheel based on a predetermined steering geometry;
• iii. receiving a second signal representative of a second toe angle of a second independently steerable wheel;
• iv. calculating an angular difference between said target toe angle and said second toe angle to create a steering command, wherein the steering command eliminates scrub of said second independently steerable wheel;
• and
• v. sending said steering command from said controller to a linear steering actuator for said second independently steerable wheel to turn said second independently steerable wheel.