Skid steer vehicle with self-leveling suspension

A skid steer loader, comprising:

• a chassis having a left side and an opposing right side, a front end and an opposing rear end, and a fore-and-aft center of gravity line;
• a lift mechanism attached to the chassis and adapted to raise and lower and attachment relative to the chassis;
• an engine fixed to the chassis;
• a first hydraulic fluid pump driven by the engine to provide hydraulic fluid under pressure;
• a second hydraulic fluid pump driven by the engine to provide hydraulic fluid under pressure;
• a third hydraulic fluid pump driven by the engine to provide hydraulic fluid under pressure;
• a first hydraulic motor in fluid communication with the first hydraulic fluid pump;
• a second hydraulic motor in fluid communication with the second hydraulic fluid pump;
• left front and left rear suspensions mounted in a fore-and-aft arrangement on the left side of the chassis for pivotal movement with respect thereto, each left suspension including:
• a left ground-engaging wheel extending from the left side of the chassis and rotationally coupled to the first hydraulic motor to be driven in rotation thereby;
• a left control arm assembly pivotably coupled to and between the left wheel and the chassis;
• a left hydraulic cylinder disposed between the chassis and the left control arm such that movement of the left control arm with respect to the chassis causes the left cylinder to extend and retract;
• a hydraulic valve coupled to and between the left hydraulic cylinder and the third hydraulic pump to regulate the flow of fluid from the third hydraulic pump to the left hydraulic cylinder;
• and
• a left suspension sensor that is responsive to changes in the position of the suspension to generate a signal indicative of the position of the suspension with respect to the chassis;
• right front and right rear suspensions mounted in a fore-and-aft arrangement on the right side of the chassis for pivotal movement with respect thereto, each right suspension including:
• a right ground-engaging wheel extending from the right side of the chassis and rotationally coupled to the second hydraulic motor to be driven in rotation thereby;
• a right control arm pivotably coupled to and between the right wheel and the chassis;
• a right hydraulic cylinder disposed between the chassis and the right control arm such that movement of the right control arm with respect to the chassis causes the right cylinder to extend and retract;
• a hydraulic valve coupled to and between the right hydraulic cylinder and the third hydraulic pump to regulate the flow of fluid from the third hydraulic pump to the right hydraulic cylinder;
• and
• a right suspension sensor that is responsive to changes in the position of the suspension to generate a signal indicative of the position of the right suspension with respect to the chassis;
• each pair of left front/right front and left rear/right rear wheels having a generally common axis of rotation;
• each pair of left front/right front and left rear/right rear control arm assemblies having a generally common pivot axis extending between the left and right sides of the chassis, both pivot axes located between and generally parallel to vertical planes through the axes of rotation of the front and rear wheel pairs and generally adjacent the fore-and-aft center of gravity line of the chassis;
• and
• an electronic controller electrically coupled to the left front, left rear, right front and right rear suspension sensors to receive the signals indicative of the positions of those suspensions and coupled to the left front, left rear, right front and right rear suspension hydraulic valves to regulate hydraulic fluid flow from the third hydraulic fluid pump into the cylinders responsive to signals received from the suspension sensors.