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122 lines
6.7 KiB
Markdown
122 lines
6.7 KiB
Markdown
# Grippers
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Grippers are mechanical devices that can be integrated with an unmanned vehicle to grip (hold) and release payloads.
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PX4 allows grippers to be triggered automatically in [Payload Delivery Missions](../flying/package_delivery_mission.md) or manually [using a Joystick](#qgc-joystick-configuration).
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:::info
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A gripper can instead be configured as a [generic RC or MAVLink actuator](../payloads/generic_actuator_control.md#generic-actuator-control-with-rc).
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A generic actuator cannot be used with a joystick or in payload missions, but it can be used with an RC Controller.
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:::
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## Supported Grippers
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There are many different gripper mechanisms ("jaws", "fingers", "electromagnets") and interfaces (PWM, CAN, MAVLink, and so on).
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PX4 supports grippers that have simple triggers to hold and release, and that use the following interfaces (see linked documents for details):
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- [PWM Servo Gripper](gripper_servo.md) - Grippers connected to autopilot PWM outputs
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- **MAVLink Gripper** (Untested) - Grippers that support the [MAV_CMD_DO_GRIPPER](https://mavlink.io/en/messages/common.html#MAV_CMD_DO_GRIPPER) MAVLink command.
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## Using a Gripper
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For information on using a gripper in missions see [Payload Delivery Missions](../flying/package_delivery_mission.md).
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You can manually trigger a gripper manually from a Joystick button if you've mapped `gripper open` and `gripper close` buttons in the [QGC Joystick Configuration](#qgc-joystick-configuration).
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Note that if you press the **Grab** button while the gripper is opening, it will automatically abort releasing behavior and go to the closed position, effectively cancelling the release command.
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If you do this in a mission while the release is actually happening, then the [delivery will be cancelled](../flying/package_delivery_mission.md#manual-control-of-gripper-in-missions).
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Manually triggering a gripper from an [RC Control](../getting_started/rc_transmitter_receiver.md) switch is not supported.
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MAVLink applications, such as ground stations, can also control the gripper using the [MAV_CMD_DO_GRIPPER](https://mavlink.io/en/messages/common.html#MAV_CMD_DO_GRIPPER) MAVLink command.
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## PX4 설정
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### Package Delivery Configuration
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PX4 gripper support is tied to the package delivery feature, which must be enabled and configured in order to be able to use a gripper.
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1. Ensure your board has the Payload Deliverer module enabled: CONFIG_MODULES_PAYLOAD_DELIVERER.
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2. Set [PD_GRIPPER_TYPE](../advanced_config/parameter_reference.md#PD_GRIPPER_TYPE) to match your gripper.
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For example, set to `Servo` for a [Servo Gripper](gripper_servo.md).
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### Gripper Actuator Mapping
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Grippers that are connected directly to a flight controller, such as PWM servo grippers, must be mapped to specific outputs during [Actuator Configuration](../config/actuators.md#actuator-outputs).
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This is done by assigning the `Gripper` function to the to the output port where the gripper is connected.
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For example, the image below assigns `Gripper` to the PWM AUX5 output.
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Additional information about actuator mapping is provided in the gripper-specific documentation.
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For example, see [Gripper Servo > Actuator Mapping](../peripherals/gripper_servo.md#actuator-mapping).
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### Enable Pre-ARM Mode
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Typically you will want to enable the [pre-arming mode](../advanced_config/prearm_arm_disarm.md).
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This mode keeps the motors disabled but allows the gripper to be opened and closed for attaching the payload (avoiding potential danger from spinning propellers).
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1. Set [COM_PREARM_MODE](../advanced_config/parameter_reference.md#COM_PREARM_MODE) to `Always`.
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### Gripper Actuation Timeout
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It is important for package delivery that the gripper has time to release before progressing to subsequent waypoints.
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For grippers that do not provide sensor-based feedback of their state, which is most of them, a configurable timeout is used to signal when the gripper _should_ have opened or closed.
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To set the actuation timeout:
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1. Measure the time taken for the gripper to open and time to close, and note the longer of these two times.
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There are two easy ways to open and close the gripper.
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While the drone is on a bench and the propellers are removed:
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- Run the `payload_deliverer` test in the QGC [MAVLink Shell](../debug/mavlink_shell.md):
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```sh
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> payload_deliverer gripper_test
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```
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::: info
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If you get an error message like "[payload_deliverer] not running", repeat the setup procedures above.
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You might also run the `payload_deliverer start` command in the Nuttx shell.
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:::
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- Use the [Joystick](#qgc-joystick-configuration) to trigger gripper open and close actions.
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2. Set [PD_GRIPPER_TO](../advanced_config/parameter_reference.md#PD_GRIPPER_TO) to whichever of the gripper open and close time is larger.
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### Mission Command Timeout
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When running a [Payload Delivery Mission](../flying/package_delivery_mission.md) it is important that the mission is not halted in the case where the gripper does not report that it has opened (or closed).
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This might happen if a gripper does not have a feedback sensor, if the feedback sensor was damaged, or if UORB dropped the gripper actuator timeout message.
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:::info
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Gripper state feedback from a sensor is not actually supported yet, but it may be in future.
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:::
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The mission command timeout provides an additional safeguard, continuing the mission if the gripper's successful actuation acknowledgement is not received.
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This timeout is also used to provide a sufficient delay for other commands to complete in the case where sensor feedback is not provided or received, such as for winch deployment/retraction, and gimbal movement to a mission-commanded orientation.
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To set the timeout:
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1. Set [MIS_COMMAND_TOUT](../advanced_config/parameter_reference.md#MIS_COMMAND_TOUT) to a value greater than the [gripper actuation timeout](#gripper-actuation-timeout).
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## QGC Joystick Configuration
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QGroundControl [Joystick](../config/joystick.md) configuration allows you to map gripper actions to Joystick buttons, after which you will be open and close the gripper manually.
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To map joystick buttons in QGroundControl:
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1. Open the menu: **QGC Logo (upper-left) > Vehicle Setup > Joystick > Button Assignment** tab.
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2. Select `Gripper Open` and `Gripper Close` actions for your desired joystick buttons, as shown above.
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You can test the actions by clicking on the mapped buttons and checking for gripper movement.
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If the gripper doesn't move as expected check the package delivery configuration and actuator mapping are set up properly.
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