Patient support device and method of operation
View Patent ↗A patient support device of a radiation therapy treatment system includes an electromechanical motor and control system for raising and lowering the support device in the Z direction. The control system utilizes regenerative braking concepts, converting the motor into a generator as the support device is lowered such that no matter the load, the support device will be lowered at a constant speed. The control system also allows for lowering of the support device in the powered off situation (i.e., when there is no power to the support device).
1. A patient support device comprising:
a base;
a table assembly supported by the base and configured to support a patient;
an actuator assembly electrically coupled to and operable to control motion of the table assembly, the actuator assembly including a motor and a brake;
a controller electrically coupled to the actuator assembly, the controller operable to generate a signal to activate the brake when power to the actuator assembly is interrupted; and
an dynamic brake assembly electrically coupled to the actuator assembly and the controller, the dynamic brake assembly operable upon deactivation of the brake, the dynamic brake assembly including a passive dynamic load module electrically coupled to the motor to increase speed of the motor,
a rectification module electrically coupled to the motor and operable to convert AC voltage to DC voltage when the AC voltage reaches a predetermined value,
a controlled dynamic load module electrically coupled to the passive dynamic load module, and
a switch operable to deactivate the brake and electrically couple the controlled dynamic load module and the actuator assembly to control a braking operation of the motor.
2. The patient support device of claim 1 wherein the motor is operable to control a substantially vertical motion of the table assembly.
3. The patient support device of claim 1 wherein the passive dynamic load module includes a capacitive dynamic load module and a resistive dynamic load module.
4. The patient support device of claim 3 wherein the passive dynamic load module further includes a voltage sensor dynamic load module.
5. The patient support device of claim 4 wherein the voltage sensor dynamic load module is operable to receive the DC voltage on the motor from the rectification module.
6. The patient support device of claim 1 wherein the controlled dynamic load module includes a current sensor dynamic load and a controlled dynamic load.
7. A radiation therapy treatment system comprising:
a patient support device including
a table assembly configured to support a patient,
an actuator assembly electrically connected to the table assembly and operable to control movement of the table assembly, the actuator assembly including a motor and a brake; and
a control system electrically connected to the actuator assembly the control system including a dynamic brake assembly operable upon release of the brake and operable to control a speed of the motor and provide linear motion of the table assembly when power to the actuator assembly is interrupted.
8. A radiation therapy treatment system of claim 7 wherein the dynamic brake assembly includes
a passive dynamic load module electrically coupled to the motor to increase speed of the motor,
a rectification module electrically coupled to the motor and operable to convert AC voltage to DC voltage when the AC voltage reaches a predetermined value,
a controlled dynamic load module electrically coupled to the passive dynamic load module, and
a switch operable to release the brake and electrically couple the controlled dynamic load module and the actuator assembly to control a braking operation of the motor.
9. The radiation therapy treatment system of claim 8 wherein the controlled dynamic load module includes a current sensor dynamic load and a controlled dynamic load.
10. The radiation therapy treatment system of claim 9 wherein the current sensor dynamic load is connected to the motor when a voltage on the current sensor dynamic load is equal to or greater than a reference voltage.