Buoyancy control system

摘要

A buoyancy-based lifting system can be dynamically controlled to lift, move, or hold a load an object of arbitrary size at a fixed depth. The control system can control the trajectory of a flexible gas-filled lift bag and attached load by opening or closing inflation and deflation valves based on ambient pressure readings obtained during a lift. Stable control can be achieved and maintained without having to directly measure the actual volume of gas in the lift bag, and without having to accumulate measurements of gas flows into and out of the bag. A controller can pre-determine limits of instability and lift control parameters, then use this information in conjunction with ambient pressure readings to prevent the system from becoming unstable during a lift. User intervention is generally unnecessary to maintain the system's instability.

主权项

1. A buoyancy-based lifting system comprising:
a flexible lift bag coupled to a load being lifted; a plurality of valves having a flow capacity, the plurality of valves including at least one inflation valve and at least one deflation valve in fluid communication with the flexible lift bag, the plurality of valves inflating or deflating the flexible lift bag by adding a compressible fluid to the flexible lift bag under control of a lift-controller; at least one pressure sensor that obtains pressure readings during a lift, the pressure readings indicating an ambient pressure external to the flexible lift bag; and the lift-controller communicatively coupled to the plurality of valves and the at least one pressure sensor, the lift-controller including a processor that determines burst durations of the plurality of valves based on an instability ratio:RS=v⁢⁢VKv⁢z  where Rs is the instability ratio, V is a velocity of the system, Kv is a valve flow rate, z is a position of the system determined based on the pressure readings, and v is an estimate of a volume of the system determined based on mass and displacement of the system and treated as a constant parameter of the system during the lift.