Electric propulsion control for transmedium unmanned vehicles, specifically automatic reconfiguration of a brushless DC motor winding termination as a function of the surrounding fluid medium.
A propulsion controller for an unmanned vehicle that operates both in air and submerged in water reconfigures the termination of a brushless DC (BLDC) motor between a star (wye) and a delta connection in response to a signal indicating the detected operating medium. A medium-detection subsystem (for example a conductivity probe, an immersion sensor, a pressure sensor, or a data-fusion estimator) classifies the surrounding fluid as air or water. When air is detected the controller commands a delta termination to favour high rotational speed for aerial flight; when water is detected the controller commands a star termination to favour high torque for higher-density submerged propulsion through a common or mechanically coupled propulsor. Switching is gated by interlocks that enforce a safe rotor state and bounded transition current. The arrangement allows a single motor and propulsor set, or a coupled set, to serve two fluid media that impose very different load characteristics, improving range and efficiency in both regimes. Star-delta switching is itself known; the disclosed advance is its automatic keying to a detected air-or-water medium in a transmedium vehicle.
Aerial rotorcraft and submerged thrusters impose opposite demands on an electric propulsor. Air is a low-density medium that rewards high propeller rotational speed, while water is roughly eight hundred times denser and rewards high torque at low speed. A motor wound and terminated for one medium is poorly matched to the other, so a vehicle that must fly and then dive either carries two separate propulsion systems, adding mass and drag, or accepts a compromise that is inefficient in both media. Reconfigurable star-delta (wye-delta) winding termination is well known as a means of trading torque for speed: industrial soft-start uses it, and switchable star-delta motor windings are described in prior art such as US5675222 and EP2421143. However, those teachings switch in response to commanded speed, load, or a manual selection. The prior art does not key the star-delta selection to an automatically detected change of operating fluid medium between air and water, because the prior art is not concerned with a vehicle that transitions between flight and submerged propulsion. As a result, no prior art uses medium classification to drive a torque-versus-speed winding reconfiguration for a transmedium drone. There remains a need for a propulsion controller that senses whether the vehicle is in air or water and automatically selects the winding termination best suited to that medium, with safe switching interlocks, so that a shared or coupled propulsor can serve both regimes efficiently.
The invention provides a method and a controller that select a BLDC winding termination as a function of a detected operating medium. A medium-detection subsystem classifies the surrounding fluid as air or water using one or more of conductivity, immersion, pressure, and fused motion or acoustic data. A switching network of contactors or solid-state switches reconfigures the motor phases between a delta connection, selected for air to favour speed, and a star connection, selected for water to favour torque. A safety interlock conditions any reconfiguration on a permitted rotor state (for example reduced or zero current, or a bounded electrical angle) and limits transition inrush. The reconfiguration may apply to a single common propulsor used in both media or to mechanically coupled air and water propulsors driven by the shared motor. Hysteresis and a confirmation dwell prevent chattering at the air-water interface. The result is improved efficiency, thrust margin, and range in each medium from a shared electrical machine, without manual mode selection by the operator.
FIG. 1 is a schematic of the transmedium vehicle showing a BLDC motor (10), a propulsor (12) which may be a common air-and-water propulsor or one of a mechanically coupled pair, a switching network (14), a medium-detection subsystem (16), and a propulsion controller (18). FIG. 2 is a wiring diagram of the switching network (14) showing the three motor phase windings and the contactor or solid-state switch set that selectively forms a star (wye) node or closes the phases into a delta loop. FIG. 3 is a torque-speed map illustrating the delta characteristic (higher speed, lower torque) overlaid with the star characteristic (lower speed, higher torque) and the operating envelopes for air and water. FIG. 4 is a flowchart of the medium-keyed switching method. FIG. 5 is a section view of an immersion and conductivity sensor (20) mounted in the airframe. FIG. 6 is a state diagram of the switching interlock. In operation, the medium-detection subsystem (16) samples one or more inputs. A conductivity probe distinguishes the high electrical conductivity of seawater from air; an immersion or wetness sensor confirms contact with liquid; a pressure sensor confirms depth consistent with submersion; and a fusion estimator (18) combines these with inertial and acoustic cues to reject spray and rain. The estimator outputs a classified medium state of AIR or WATER with a confidence value. The controller (18) requires the confidence to exceed a threshold and the state to persist for a confirmation dwell before commanding a change, providing hysteresis at the interface. When AIR is confirmed, the controller commands the switching network (14) to the delta termination so the motor (10) develops high rotational speed suitable for aerial thrust. When WATER is confirmed, the controller commands the star termination so the same or coupled propulsor develops high torque suitable for the denser medium. Before any reconfiguration, the interlock of FIG. 6 brings the motor to a permitted rotor state, for example commanding a current reduction or a brief freewheel so that switches operate within rated transition current. The controller then ramps current back up in the new termination. In an embodiment the switching network uses make-before-break sequencing on solid-state devices to bound transient torque. In a further embodiment the star or delta selection is additionally trimmed by commanded thrust so that, within a medium, the controller may bias the termination, while the primary selection key remains the detected medium.
| Patentability | 86.0% |
| Prior-art position | 64.0% |
| Technical merit | 64.0% |
| Commercial | 74.0% |
| Composite genius score | 74.2/100 (Promising) |