Performance Specifications
Flight behaviors and ACE system specifications
Landing Target Detection
ACE is capable of detecting a wide range of fiducial target sizes and patterns. The size of the fiducial directly affects the maximum altitude at which ACE can reliably detect and track the landing target. Planck offers a standard 76cm target which affords an 20m+ detection altitude, though various parameters of the system can be changed to increase detection altitude at the expense of speed. Contact Planck for custom target sizes and configurations for increased detection altitude.
For a default configuration in normal lighting conditions, ACE will detect the fiducial target at 20-30hz, and provide updates to its internal estimator, or the autopilot in the case of Guidance-only mode, at 100hz (configurable).
Full-Control Flight Behaviors
Takeoff
During takeoff, the aircraft will ascend directly above the landing target until it reaches is maximum tracking height that is free and clear of obstructions on the vehicle or vessel.
The aircraft ascends most rapidly immediately after takeoff, before settling into a constant rate. During the ascent, the aircraft will also adjust yaw to maintain the same relative heading as the vehicle or vessel it is tracking (configurable).
Ascent Rate: 1 m/s (default), 0.1 m/s - 2 m/s (configurable)
Parameter | Default | Configurable Range |
Ascent Rate | 1 m/s | 0.1 - 2 m/s |
Takeoff Altitude | 10 meter | 0 - 20+* meters |
*higher takeoff altitudes may require GPS and additional configuration
Landing
During landing, ACE will position the aircraft directly above the landing target from its approach altitude, yaw the aircraft relative to the landing target, and then descend and execute the landing maneuver. The descent rate will vary based on operating conditions, including wind and motion of the landing platform. At the very end of the sequence, the aircraft will descent very quickly.
Parameter | Default | Configurable Range |
Approach Altitude | 10 meters | 3 - 20+* meters |
Descent Rate | 0.5 m/s | 0.1 - 2 m/s |
Fast Descent Altitude | 0.7 m | 0 - 2 meters** |
*higher approach altitudes may require GPS and additional configuration
** The ideal fast descent altitude is different for each aircraft and scenario and should be configured accordingly.
Return to Base (RTB)
At the end of a mission, or when commanded, the aircraft will turn toward the host vehicle and traverse a course that is optimized to minimize flight time while intercepting the moving landing platform. The intercept course is continually updated based on the motion of the host vehicle. Depending on the speed and direction of the host vehicle, the aircraft will adjust its heading and speed as it approaches, before transitioning to land.
The transit rate during the RTB portion of flight can be configured based on the aircraft capabilities and mission profiles.
Wingman
In Wingman mode, the aircraft will hold a position (bearing and range) relative to the host vehicle as it moves. The aircraft will match the speed and direction of the host vehicle. However, in many cases it may be possible for the host vehicle to exceed the speed capability of the aircraft.
GPS
GPS is not required for ACE takeoff and landing operations from moving platforms. Standard GPS or other localization method is required for RTB, Wingman, and waypoint flight.
For tethered operations, GPS is not required for precision station-keeping. However, the operational envelope may be extended with GPS during tethered operations.
Terrain
ACE is compatible with terrain models for flying in diverse terrain if supported by the autopilot.
Operational Envelope
The operational envelope is governed more by the performance of the aircraft than the ACE system. ACE issues very precise, high rate control inputs to the aircraft's autopilot, but it is up to the aircraft to successfully execute those commands. For example, the maximum speed of a boat during landing is a function of the maximum speed of the aircraft and the aircraft's control authority at that speed. The operational envelope for any given system should be determined through testing during the integration process.
The specifications in the table below are typical for ACE integrated into a UAV in a standard configuration. These assume that the aircraft has been carefully tuned for optimal performance and that ACE has been configured for the specific aircraft.
Parameter | Performance | Notes |
Landing accuracy | 10 - 15 cm typical | |
Vehicle speed during landing | 50% of UAV max speed | Includes relative wind |
Sea State | 3 on small craft | Rolling, pitching, and heaving* |
Target detection range | 20 m (65 ft) Option for 40m (130ft) | Range scales based on size of landing target |
Night operation | Yes - full operation | Requires visible or IR illumination |
Rain | Yes - full operation | Landing target must be visible |
Fog | Yes - full operation | Requires at least 20 meters visibility. Can be augmented with additional IR illumination or GPS. |
*ACE accounts for the heave of a dynamically moving landing platform, and it adjusts the descent rate accordingly. Timing the landing is crucial for safe and reliable operations, and ACE commits to a landing maneuver when the platform is within operational limits. If those limits are exceeded, the aircraft will perform a failsafe behavior.
Failsafe Behaviors
ACE includes failsafe behaviors are that specific for operating from moving vehicles and vessels.
Failsafe | Behavior |
Loss of communications | Return to last known host vehicle location and hold position |
Low power | RTB and land on host vehicle |
Unsuitable Landing Location or Motion | Abort landing Hold relative position Ascend and restart |
Loss of landing target | Pause descent Ascend and restart |
Reliability
ACE was developed over several years and thousands of real-world flights by experts in robotics, controls, and computer vision. UAS using ACE experience virtually no failed landings if within the operational envelope. ACE is intelligent enough to abort unsafe landings. Since it is more than a positioning system, ACE uses the state of the aircraft and landing platform, as well as timing, to execute landings at the right time. Planck has conducted thousands of UAV landings with >95% within 15cm of the center of the landing platform, even while moving. The vision-based navigation system is:
Robust to partial occlusions of the landing target
Adjusts to shadows and changing lighting conditions
Works in low-light conditions with visible or IR illumination
Robust to optical distortion, fuzziness, and difficult lighting conditions
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