Reducing swing of model helicopter sling load using input shaping

Abstract

Helicopter sling-load operations are extremely useful, but they can also be dangerous. Excessive swinging of the load can degrade control, cause the payload to collide with obstacles, or allow the suspension cable to get tangled with objects. Suppressing load swing could increase safety and productivity. Input shaping is a control technique that has been used to suppress vibration of flexible machines, such as robots, satellites, and cranes. To investigate the use of input shaping on helicopters, a dynamic model is formed to characterize the translational response of a model helicopter and sling load to lateral control inputs. This translational model is used to simulate point-to-point movements with and without input shaping for a range of move distances. The input-shaped movements show greatly-reduced residual swing, with only a minor increase in move time. Data from an experimental trial using a model helicopter is presented.

An experimental remote-controlled helicopter with suspended load

“…Researchers have developed control systems that mitigate the detrimental effects of suspended load swing. Some example control strategies have included input shaping [11,5,12], cable angle feedback [13,14], and a combination of both [15,16].…”

Reduced-modification input shapers for manually controlled systems with flexibility

“…It has been applied to problems like liquid sloshing [8], [9] and helicopter load swing [10], [11]. Manual-tracking experiments have shown that input shaping can significantly reduce tracking error and subjective difficulty when controlling a flexible element [12].…”

Spot hover control of helicopter and swing control of helicopter sling load by using Zhang-gradient method

“…It reduces not only the efficiency of the transportation, but also the safety factor of helicopter [5]. When the load oscillates, it is very difficult to guarantee the safety of helicopter only depending on the pilot's skills [3,[6][7][8]. Therefore, a controller is needed to reduce the swing of load, which can reduce the pressure of the pilot and provide the security assurance of helicopter.…”

“…What is more, the helicopter is not subject to the sites, because it does not need a dedicated airport. As a result, the helicopter sling load has been widely used in various aspects [2][3][4]. However, during the transportation, the load has the similar movement to the simple pendulum, i.e., oscillation.…”

“…The control of helicopter sling load system is a heated topic [1][2][3]. The simplified model of a helicopter sling load system is plotted in Fig.…”