Motion enable mechanism with capacitive sensor
A motion-enable device includes a mechanical switch and a capacitive sensor with a sensing region that is located adjacent to the mechanical switch. The mechanical switch enables a first signal when closed or actuated that indicates that the mechanical switch is in an active state. The capacitive sensor enables a second signal when a conductive object is disposed in the sensing region, where the second signal indicates that the capacitive sensor is in an active state. Enablement of operation of an apparatus depends on receipt of both the first signal and the second signal. The mechanical switch and the capacitive sensor act as the two separate switches required by functional safety requirements for a motion enable device. Because the sensing region of the capacitive sensor is adjacent to the mechanical switch, the first and second signals are generated when an operator actuates the mechanical switch with a single digit.
1. A method of enabling motion of an apparatus having a capacitive sensor, a mechanical switch, a power source, and an actuator with a motor driver circuit, the method comprising:
receiving a sensor active signal from the capacitive sensor when a conductive object is disposed in a sensing region of the capacitive sensor;
while receiving the sensor active signal, determining whether a switch active signal is received from the mechanical switch when the mechanical switch is actuated from a first position to a second position;
based on receipt of the sensor active signal and a determination that the switch active signal from the mechanical switch is not enabled, establishing a power connection between the power source and the motor driver circuit;
while the power connection between the power source and the motor driver circuit is established, receiving the switch active signal; and
in response to receiving the switch active signal, enabling transmission of motion control signals to the motor driver circuit.
2. The method of claim 1 , further comprising, prior to enabling the transmission of motion control signals, determining no faults are currently detected that are associated with the actuator.
3. The method of claim 2 , further comprising: determining a target motion trajectory for the actuator; and transmitting motion control signals to the motor driver circuit for causing the actuator to generate an output motion that follows the target motion trajectory for the actuator.
4. The method of claim 1 , wherein the capacitive sensor and the mechanical switch are included in a single motion-enable device.
5. A motion-enable system, comprising:
an actuator;
a mechanical switch that includes an interface surface that is disposed on a first side and configured to receive a physical input and a second side that is different from the first side, wherein the mechanical switch is configured to enable a first signal when the mechanical switch is actuated from a first position to a second position by the physical input, and wherein the first signal indicates that the mechanical switch is in a first active state;
a capacitive sensor with a sensing region that extends past the interface surface of the mechanical switch, wherein the capacitive sensor is configured to enable a second signal when a conductive object is disposed in the sensing region and the second signal indicates that the capacitive sensor is in a second active state, and
a controller configured to:
receive the second signal;
in response to receiving the second signal, establish a power connection between a power source and a motor driver circuit of the actuator;
while receiving the second signal, receive the first signal; and
in response to receiving the first signal while receiving the second signal, enable motion of the actuator,
wherein at least a portion of the mechanical switch is disposed between the interface surface and the capacitive sensor and prevents the user digit from contacting the capacitive sensor.
6. The motion-enable system of claim 5 , wherein the capacitive sensor is configured with an extended sensing region that extends beyond the sensing region that extends past the interface surface.
7. The motion-enable system of claim 6 , wherein the controller is further configured to, after enabling the second signal, continue to enable the second signal when the conductive object is disposed in the extended sensing region and is no longer disposed in the sensing region that extends past the interface surface.