Controlling motion position of multi-leaf collimator

A method of controlling a motion position of a multi-leaf collimator, comprising:

• transmitting a control signal to a first motor to drive a trolley to move, the trolley being movably connected to a first screw rod and carrying a row of leaves arranged on a side of the multi-leaf collimator;
• receiving first position information of the trolley from a first encoder arranged on the first motor;
• receiving second position information of the trolley from a displacement sensor arranged on the first screw rod;
• receiving third position information of the trolley from a limit switch when the trolley is at an origin position, wherein the limit switch is located on an end of the first screw rod;
• receiving motion position information of the trolley detected by a first approaching switch when the trolley moves along the first screw rod to the first approaching switch, wherein the first approaching switch is located between the limit switch and a center of the first screw rod and has a preset distance with the limit switch;
• comparing the first position information with the second position information to determine whether the first position information is coincident with the second position information;
• and
• when the first position information is determined not to be coincident with the second position information, adjusting a rotation angle of the first motor to correct a deviation of the motion position of the trolley.

A linear accelerator comprising:

• a multi-leaf collimator having two rows of leaves arranged on opposite sides;
• and
• a motion position controlling device comprising:
• a control system;
• two trolleys connected with the control system, wherein each of the trolleys carries a respective row of the leaves and is movably connected with a first screw rod and driven by a first motor connected with the first screw rod;
• a first encoder arranged on the first motor and operable to feed back first position information of the trolley to the control system;
• a displacement sensor arranged on the first screw rod and operable to feed back second position information of the trolley to the control system, wherein the control system is operable to control the motion position of the trolley based on the first position information and the second position information;
• a limit switch arranged on at least one end of the first screw rod, wherein the limit switch is in communication with the control system;
• and
• a first approaching switch arranged between a center of the first screw rod and the limit switch in a way that the first approaching switch has a preset distance with the limit switch, wherein the first approaching switch is in communication with the control system.