Although several studies have revealed that fractional order controllers usually outperform conventional integer-order control solutions, fractional order controllers are not yet widely applied in industrial applications due to their complex mathematical background. In this paper, further improvements of a simple weighted sum feedback design are introduced that imitates the behavior of a fractional order controller but is free from its various formal restrictions. The proposed control solution has the main characteristics of a fractional order controller, such as finite memory length, excellent transient response with no overshoot and robust behavior, but it is placed into a much simpler mathematical framework. In the current paper, a simple derivative term was incorporated in the design which made the controller’s output more stable by completely eliminating output chattering. The proposed control method was developed for a general second-order system. It was tested in a fixed point iteration-based adaptive control scenario, through simulations using a robotic example and on experimental basis as well, utilizing a simple one-degree-of-freedom electromechanical system. The presented experiments are the first systematic investigations of the fixed point iteration-based adaptive control method.

In this paper the first attempt is introduced in a series of investigations on improving the control performance of a Fixed Point Iteration-based adaptive control scenario in a motor control application. As it is well know, due to quantization error of the position measurement in case of an incremental encoder, the estimated velocity and acceleration feedback signal has various high frequency noise components, which can degrade the control performance. In this paper a simple low pass filter design will be used to filter the output of the controller. It was shown on experimental basis that such filter could improve efficiency of the controller without compromising the trajectory tracking error. The control performance is also improved by introducing a simple conditional integral in the feedback design, to avoid high overshoots at the beginning of the control.

In the field of life sciences, delay effects are often modeled with two compartments that do not model any particular organ. In this paper the use of this double counterpart model is investigated in Fixed-Point Iteration-based (FPI) Control, which was introduced in 2009 as an adaptive extension to the Computed Torque Control method. This controller is particularly sensitive to delays and measurement noise due to its iterative nature. It was recognized that, besides modeling the delay effect, this signal tackling also provided the controller with some noise filtering ability; the formerly accumulated effects of noise filtering and formally delayed sampling were avoided. This smeared delay has a noticeable effect even slightly later in time, making the adaptive method based on it more robust. This assumption was investigated both on a simulation and experimental basis.