Patient transport apparatus with auxiliary wheel control systems

A patient transport apparatus comprising:

• a support structure;
• a support wheel coupled to the support structure, with the support wheel being swivelable about a swivel axis;
• and
• an auxiliary wheel system including:
• an auxiliary wheel coupled to the support structure to influence motion of the patient transport apparatus over a floor surface;
• an auxiliary wheel drive system including:
• a motor coupled to the auxiliary wheel to rotate the auxiliary wheel relative to the support structure at a rotational speed;
• and
• a motor control circuit for transmitting power signals from a battery to the motor;
• a user interface including a throttle assembly positionable between a neutral throttle position and a plurality of operating throttle positions, each operating throttle position of the plurality of operating throttle positions being associated with a rotation speed value of the auxiliary wheel;
• and
• a control system coupled to the user interface and the auxiliary wheel drive system for operating the auxiliary wheel drive system based on the plurality of operating throttle positions, the control system including a controller configured to:
• detect a current operating throttle position of the throttle assembly,
• determine a desired rotational speed value associated with the current operating throttle position,
• determine a current rotational speed of the auxiliary wheel,
• select an acceleration rate from a plurality of acceleration rates based on the current rotational speed of the auxiliary wheel,
• monitor an electrical current draw from the battery by the motor,
• monitor an electrical current through motor phase windings of the motor,
• generate an output signal based on the selected acceleration rate, the monitored electrical current draw from the battery by the motor, and the monitored electrical current through the motor phase windings of the motor, and
• transmit the generated output signal to the motor control circuit to operate the motor to rotate the auxiliary wheel at the selected acceleration rate;
• wherein the controller includes a plurality of control loop modules, including:
• a speed loop module configured to generate a speed loop signal based on the selected acceleration rate,
• a battery current loop module configured to generate a high battery current signal and a low battery current signal based on the monitored electrical current draw from the battery,
• a motor phase current loop module configured to generate a high motor phase current signal and a low motor phase current signal based on the monitored electrical current through the motor phase windings of the motor,
• an output generation module configured to select one of the speed loop signal, the high battery current signal, the low battery current signal, the high motor phase current signal, and the low motor phase current signal as the output signal;
• and
• wherein the output generation module is configured to determine if the speed loop signal is above a zero signal value and responsively select one of the speed loop signal, the high battery current signal, and the high motor phase current signal having a smallest signal value as the output signal.

A patient transport apparatus comprising:

• a support structure;
• a support wheel coupled to the support structure, with the support wheel being swivelable about a swivel axis;
• and
• an auxiliary wheel system including:
• an auxiliary wheel coupled to the support structure to influence motion of the patient transport apparatus over a floor surface;
• an auxiliary wheel drive system including:
• a motor coupled to the auxiliary wheel to rotate the auxiliary wheel relative to the support structure at a rotational speed;
• and
• a motor control circuit for transmitting power signals from a battery to the motor;
• a user interface including a throttle assembly positionable between a neutral throttle position and a plurality of operating throttle positions, each operating throttle position of the plurality of operating throttle positions being associated with a rotation speed value of the auxiliary wheel;
• and
• a control system coupled to the user interface and the auxiliary wheel drive system for operating the auxiliary wheel drive system based on the plurality of operating throttle positions, the control system including a controller configured to:
• detect a current operating throttle position of the throttle assembly;
• determine a desired rotational speed value associated with the current operating throttle position;
• determine a current rotational speed of the auxiliary wheel;
• select an acceleration rate from a plurality of acceleration rates based on the current rotational speed of the auxiliary wheel;
• monitor an electrical current draw from the battery by the motor;
• monitor an electrical current through motor phase windings of the motor;
• generate an output signal based on the selected acceleration rate, the monitored electrical current draw from the battery by the motor, and the monitored electrical current through the motor phase windings of the motor;
• and
• transmit the generated output signal to the motor control circuit to operate the motor to rotate the auxiliary wheel at the selected acceleration rate;
• and
• wherein the controller includes a plurality of control loop modules, including:
• a speed loop module configured to generate a speed loop signal based on the selected acceleration rate;
• a battery current loop module configured to generate a high battery current signal and a low battery current signal based on the monitored electrical current draw from the battery;
• and
• an output generation module configured to select one of the speed loop signal, the high battery current signal, and the low battery current signal as the output signal.