Fig 1.
Various exterior wall cleaning robots (a) Tito [8] (b) IPC EAGLE [9, 10] (c) SKYPRO [11, 12] (d) Gecko [12–15].
Fig 2.
Configuration of winch-mounted wall-climbing robot [39, 40].
The robot largely consists of three parts: a propeller thrust unit, winch unit, and cleaning and frame unit. The cleaning unit is placed at the bottom of the robot considering water leakage. a) Overview of winch-mounted wall-climbing robot (b) Assembly of the winch unit and cleaning and frame unit.
Fig 3.
A flat-type nozzle displays good spray uniformity.
In terms of impact efficiency, it displays higher cleaning performance than those of hollow-cone- or full-cone-type of nozzle. (a)–(c) are flat nozzle tips. Their spray angles are 15°, 25°, and 40° respectively, (d) spray angle of 40° at 6 bar [35, 36].
Fig 4.
Control parameters (a–c) and a user condition (d). a) Nozzle inlet pressure, b) Spray distance, c) Spray angle. d) Cleaning speed of the robot [29, 37].
Table 1.
Control parameters and user condition for optimization of the cleaning device.
Fig 5.
Device setup for the image data measurement and conversion to image data from the test results.
a) Device setup to capture photographs for the image data, b) A test result photograph after cleaning, c) Image data converted from the photographs [29, 38].
Table 2.
L9(33) orthogonal array and evaluation results of image data.
Fig 6.
The test bench consists of two parts: A cleaning performance evaluation unit for investigating spray characteristics and a nozzle spray unit for implementing movement of the robot for cleaning.
Each unit has a load cell to measure the reaction force and impact force. (a) Overall schematic of test bench and that of (b) the water spray unit.
Fig 7.
Experimental test bench setup for evaluating the cleaning performance.
a) Test scenario with high-pressure water cleaning, b) Cleaning performance evaluation unit and transfer devices in two directions (X, Y). c) Water-spray-unit assembly. Specifications of main parts: Pump: 8905-902-290(SHURflo), Pressure sensor: GP-M025, (KENYCE), Load cell: BCA-5(CAS), Nozzle: Flat type, HM_V5 (Hanmi Nozzle.co.Ltd) [35].
Fig 8.
Sensitivity analysis results of the control parameters based on Eq (2).
Fig 9.
Test results for the highest and lowest cleaning performances.
The highest performance results were those of Exp.#7 (Table 2) for the user condition of 3 m/min, as shown in a)–c). d)–f) display the results for 6 m/min. The worst performance result was for Exp. #6 under both the user conditions (3 mm/s and 6 mm/s).
Fig 10.
The results of verification test performed under the optimal conditions.
Nozzle inlet pressure: 8 bar; spray distance: 0.2 m; injection angle: 40°. Image data results: 74.8% (average).
Fig 11.
Reaction force on nozzle and impact force on panel under the condition of 8 bar, 0.3 m, 15°.