Abstract: Disclosed are a power assembly and a surface-cleaning device. The power assembly includes a power source configured to provide fluid power; and a silencing cavity arranged around the power source. The silencing cavity has an axial depth and a radial depth. The radial depth is configured to eliminate noise within a first frequency range, and the axial depth is configured to eliminate noise within a second frequency range; and the axial depth is at least 20 mm but not more than 120 mm.

Abstract: A ranging apparatus includes: a light emitter (101) and at least two photodetectors. The light emitter (101) is configured to emit probe light. The at least two photodetectors include a first photodetector (102) and a second photodetector (103). The first photodetector (102) is configured to receive first signal light reflected by a to-be-detected target (100) under the action of the probe light and output a first echo signal; the second photodetector (103) is configured to receive second signal light reflected by the to-be-detected target (100) under the action of the probe light and output a second echo signal, thereby obtaining a target distance based on the ratio of the first echo signal to the second echo signal.

Abstract: A cliff sensor and a self-moving device. The cliff sensor comprises an optical emitter and an optical receiver, an emission light path of the optical emitter being provided with a first convex lens, a partition plate being arranged between the optical emitter and the optical receiver, a portion on the first convex lens close to the partition plate being provided with a first total-reflection structure, the first total-reflection structure being used for totally reflecting first light rays, and the first light rays being part of light rays emitted by the optical emitter and, in the first convex lens, emitted to the partition plate.

Abstract: A distance measuring device is applicable to a sweeping robot and includes a signal source disposed near a front end edge of a bottom surface of the sweeping robot and configured to transmit a cone-shaped detection signal at a preset angle; a first signal receiver disposed at a first position near the signal source and configured to receive a reflected signal of the cone-shaped detection signal reflected by the ground, wherein the first position is a corresponding position when a projected area of the cone-shaped detection signal on the ground is maximum; and a second signal receiver disposed at a second position near the first signal receiver and configured to receive a reflected signal of the cone-shaped detection signal reflected by a cliff surface, wherein the second position is a corresponding position when a projected area of the cone-shaped detection signal on the cliff surface is maximum.