Auto guide vehicle
An auto guide vehicle ( 20 ) that conveys a cart ( 10 ), wherein the auto guide vehicle ( 20 ) is provided with: a fluid pressure cylinder ( 22 ) that is able to be extended and retracted vertically, and that applies an upward pressing force to the floor surface of the cart ( 10 ); a fluid pressure supply device ( 70 ) that supplies a fluid to the fluid pressure cylinder ( 22 ); pressure regulating means ( 50 ) that regulates the fluid pressure of the fluid supplied from the fluid pressure supply device ( 70 ) to the fluid pressure cylinder ( 22 ); a control board ( 40 ) that outputs a fluid pressure command value to the pressure regulating means ( 50 ); and a pressure sensor ( 100 ) that detects the fluid pressure of the fluid supplied to the fluid pressure cylinder ( 22 ); wherein the control board ( 40 ) computes derivatives of the fluid pressure detected by the pressure sensor ( 100 ), estimates a timing at which the cart begins to leave the ground based on a pattern of the computed derivatives, and computes the command value by multiplying a coefficient less than one by the fluid pressure detected by the pressure sensor ( 100 ) at the estimated timing.
1. An auto guide vehicle that conveys a cart by being ensconced in a standard space formed between a floor surface and a bottom surface of the cart, wherein the auto guide vehicle is provided with:
a fluid pressure cylinder that is able to be extended and retracted vertically, and that applies an upward pressing force to the bottom surface of the cart;
a fluid pressure supply device that supplies a fluid to the fluid pressure cylinder;
pressure regulating means that regulates the fluid pressure of the fluid supplied from the fluid pressure supply device to the fluid pressure cylinder;
a control board that outputs a fluid pressure command value to the pressure regulating means; and
a pressure sensor that detects the fluid pressure of the fluid supplied to the fluid pressure cylinder; wherein
the control board comprises:
a differentiation circuit that computes derivatives of the fluid pressure detected by the pressure sensor;
an estimation circuit that, based on a pattern of the derivatives computed by the differentiation circuit, estimates a timing at which the cart begins to leave the ground; and
a coefficient multiplication circuit that computes the command value by multiplying a coefficient less than one by the fluid pressure detected by the pressure sensor at the timing estimated by the estimation circuit.
2. The auto guide vehicle as in claim 1 , wherein:
the fluid pressure cylinder is formed by inserting a piston into a cylinder body so as to be able to move vertically, a receiving plate that contacts the bottom surface of the cart is provided on an upper end of a piston rod connected to the piston, and a proximity switch that switches on upon approaching to within a certain distance from the bottom surface of the cart is provided on the receiving plate; and
the estimation circuit estimates the timing at which the cart begins to leave the ground as being a time at which, with the proximity switch switched on, the derivative computed by the differentiation circuit has risen to a first prescribed value or higher, then fallen to a second prescribed value or lower.
3. The auto guide vehicle as in claim 1 , wherein the estimation circuit estimates the timing at which the cart begins to leave the ground as being a time at which, after a certain period of time has elapsed since the fluid pressure cylinder began to extend, the derivative computed by the differentiation circuit has risen to a first prescribed value or higher, then fallen to a second prescribed value or lower.
4. The auto guide vehicle as in claim 1 , wherein the estimation circuit estimates the timing at which the cart begins to leave the ground as being a time at which the derivative computed by the differentiation circuit becomes approximately zero.
5. The auto guide vehicle as in claim 1 , wherein:
when there are multiple fluid pressure cylinders, the pressure regulating means and the pressure sensor are respectively provided on respective fluid pressure cylinders; and
the coefficient multiplication circuit respectively outputs, to the respective pressure regulating means, command values corresponding to the pressures detected by the respective pressure sensors.