Follow-up steering control system for multi-axle automobile crane, and multi-axle automobile crane

A follow-up steering control system for a multi-axle automobile crane, the multi-axle automobile crane comprising an active steering rear axle (9), a rear left steering wheel (11) and a rear right steering wheel (15) mounted on the active steering rear axle (9), a first knuckle arm (17) for controlling the steering of the rear left steering wheel (11), a second knuckle arm (18) for controlling the steering of the rear right steering wheel (15), and an oil return circuit, the follow-up steering control system comprising:

• a left-turning hydraulic cylinder (8), a right-turning hydraulic cylinder (13), a first control valve device (7), a middle-position locking hydraulic cylinder (10), a second control valve device (12), a front axle steering detection device, a rear axle steering detection device, an automobile speed detection device and a control device, wherein, a piston rod of the left-turning hydraulic cylinder (8) and the bottom end of the cylinder block of the left-turning hydraulic cylinder are hinged with the active steering rear axle (9) and the first knuckle arm (17) respectively;
• a piston rod of the right-turning hydraulic cylinder (13) and the bottom end of the cylinder block of the right-turning hydraulic cylinder are hinged with the active steering rear axle (9) and the second knuckle arm (18) respectively;
• a first oil pressure output port (A) of the first control valve device (7) is communicated with a rodless cavity of the left-turning hydraulic cylinder (8) and a rod cavity of the right-turning hydraulic cylinder (13);
• a second oil pressure output port (B) of the first control valve device (7) is communicated with a rod cavity of the left-turning hydraulic cylinder (8) and a rodless cavity of the right-turning hydraulic cylinder (13);
• the middle-position locking hydraulic cylinder (10) comprises a middle-position locating block (28) fixedly arranged in a cylinder block (21) and a first piston (22) and a second piston (29) arranged on both sides of the middle-position locating block (28) respectively, wherein, the first piston (22) is fixedly connected with a piston rod, the inner cavity of the cylinder block (21) is separated into a rod cavity (25), a middle cavity (24) and a rodless cavity (26) by the first piston (22) and the second piston (29), the piston rod (23) of the middle-position locking hydraulic cylinder (10) and the bottom end of the cylinder block (21) are hinged with the active steering rear axle (9) and one of the first knuckle arm (17) and the second knuckle arm (18) respectively;
• a third oil pressure output port (T2) of the second control valve device (12) is communicated with the middle cavity (24), and a fourth oil pressure output port (D) is communicated with the rodless cavity (25) and the rod cavity (26) of the middle-position locking hydraulic cylinder (10), the third oil pressure output port (T2) is always communicated with the oil return circuit, in the case where the multi-axle automobile crane travels forward, the fourth oil pressure output port (D) outputs a high pressure and the third oil pressure output port (T2) is communicated with the oil return circuit;
• in the case where the multi-axle automobile crane turns, both the third oil pressure output port (T2) and the fourth oil pressure output port (D) are communicated with the oil return circuit;
• wherein, in the case where the lowest speed limit value of an automobile is detected by the automobile speed detection device, the front axle steering detection device detects that the front axle is located at a middle position, and the rear axle steering detection device detects that the active steering rear axle (9) is located at the middle position, the control device controls the middle-position locking hydraulic cylinder to be in an unlocked state.