Abstract for: Control Heuristics for Soft Landing Problem
In this paper, we developed two different control heuristics for the soft landing problem. The first heuristic is adapted from the mass spring damper model using the similarity of the equations of the soft landing model given in this paper to the equations of the mass spring damper model; both models can be reduced to a second order linear differential equation. The second one is a bang-bang heuristic that first allows the spacecraft to fall freely, but after a critical point is reached, it uses the reverse force thruster at its maximum power until the touchdown. Bang-bang heuristic minimizes the time needed to land. However, it may crash the spacecraft in the presence of an error in the parameter estimates, or an error in the velocity or height readings, or an overlooked factor such as a delay in changing the level of the force created by the reverse force thruster, which is known as actuator delay. The mass spring damper based control heuristic requires a longer landing time, but it is more robust compared to the bang-bang control heuristic in the sense that it is less sensitive to the errors in parameter values, errors in readings, and presence of an actuator delay.