A suspended-type smart painting apparatus for a building wall surface, comprising a support (1), a painting mechanism (2), a suspension and movement mechanism (3), a control mechanism (4), and a paint storage mechanism (5). The support (1) comprises a support main body (11), and an auxiliary support (12). The painting mechanism (2) comprises a support arm (21), a painting spray head (22), and a roller (23). The suspension and movement mechanism (3) comprises a reel (31), a horizontal plate (32), horizontal movement mechanisms (33) arranged at two ends of the horizontal plate (32), and a first motor (34). Each horizontal movement mechanism (33) comprises a roller wheel (331), a second motor (332), and a transmission gear (333). The control mechanism (4) comprises a microcontroller (42), an air pump (43), and a sensor group (41). The paint storage mechanism (5) comprises a storage drum (52), a one-way air valve (51), a stirring rod (53), an electromagnet array (56), and a paint outlet (57). The suspended-type smart painting apparatus for a building wall surface is reasonable in structure, has advantages such as being simple in structure, convenient to use, safe and reliable, and convenient to convey materials, and effectively solves the problem that painting high walls is unsafe.

A coating device includes a conveyor, a driver, circuitry, and a digital-to-analog converter. The conveyor includes a coating roller to coat a medium with a liquid while conveying the medium in a conveyance direction. The driver rotates the coating roller at a rotation speed. The circuitry outputs a speed command value as a digital value. The digital-to-analog converter converts the speed command value as the digital value into an analog voltage value. Further, the circuitry calculates a correction amount to correct the speed command value, reflects the correction amount in the speed command value when the medium is not passing through the coating roller, and applies the speed command value, as the analog voltage value corrected by the correction amount, to the driver to rotate the coating roller at the rotation speed to convey the medium.