Donghong Ning

An active seat suspension design for vibration control of heavy-duty vehicles

This paper presents the design, fabrication and testing of an innovative active seat suspension system for heavy-duty vehicles. Rather than using conventional linear actuators, such as hydraulic cylinders or linear motors, which need to be well maintained and are always expensive when high force outputs are required, the proposed seat suspension system directly applies a rotary motor in order to provide the required active actuation, without changing the basic structure of the existing off-the-shelf seat suspension. A gear reducer is also applied to amplify the output torque of the motor so that a high output torque can be achieved using a low rated power motor. A static output feedback H ∞ controller with friction compensation is designed to actively reduce seat vibration. Experiments are carried out to test the fabricated suspension prototype. The experimental results show that this type of seat suspension can achieve greater ride comfort in the frequency range of 2–6 Hz than a passive seat suspension. The newly designed active seat suspension is much more cost effective and can be suitable for heavy-duty vehicles.

Takagi–Sugeno Fuzzy Control for Semi-Active Vehicle Suspension With a Magnetorheological Damper and Experimental Validation

Much research has gone into developing advanced control algorithms for semi-active suspension. Experimental validation of these control algorithms is critical for their practical applications. This paper investigates a state-observer-based Takagi–Sugeno fuzzy controller (SOTSFC) design for a semi-active quarter-car suspension installed with a magnetorheological (MR) damper and provides proof of the effectiveness of the proposed controller. To conduct the test, a quarter-car test rig and control system hardware were used. Then, a new MR damper was designed and built to fit with the test rig. After that, the SOTSFC for the quarter-car test rig was developed. Finally, several tests were conducted on the quarter-car suspension in order to investigate the real effect of the SOTSFC. It was then compared with the use of a skyhook controller to demonstrate its benefits.

Relaxed fuzzy observer‐based output feedback control synthesis of discrete‐time nonlinear control systems

This work develops the development of observer-based output feedback control design of discrete-time nonlinear systems in the form of Takagi–Sugeno fuzzy model. Lately, previous results have been improved in virtue of a two-step method. From a technical point of view, it is not flawless and related problems have not been completely resolved. In this study, more advanced two-steps approach is further developed while the relative sizes among different normalized fuzzy weighting functions are utilized by introducing some additional matrix variables. As a result of the above work, those main defects of the existing method can be redressed and a desired solution in aspect of not only reducing the conservatism but also alleviating the computation complexity is provided for some special cases. Moreover, the effectiveness of the proposed result is shown at length by means of an illustrative example.

Integrated active and semi-active control for seat suspension of a heavy duty vehicle:

In this article, an integrated active and semi-active seat suspension for heavy duty vehicles is proposed, and its prototype is built; an integrated control algorithm applied measurable variables (suspension relative displacement and seat acceleration) is designed for the proposed seat prototype. In this seat prototype, an active actuator with low maximum force output (70 N), which is insufficient for an active seat suspension to control the resonance vibration, is applied together with a rotary magnetorheological damper. The magnetorheological damper can suppress the high vibration energy in resonance frequency, and then a small active force can further improve the seat suspension performance greatly. The suspension’s dynamic property is tested with a MTS system, and its model is identified based on the testing data. A modified on–off controller is applied for the rotary magnetorheological damper. A H ∞ controller with the compensation of a disturbance observer is used for the active actuator. Considering the energy saving, the control strategy is designed as that only when the magnetorheological damper is in the off state (0 A current), the active actuator will have active force output, or the active actuator is off. Both simulation and experiment are implemented to verify the proposed seat suspension and controller. In the sinusoidal excitations experiment, the acceleration transmissibility of integrated control seat has lowest value in resonance frequency and frequencies above the resonance, when compared with power on (0.7 A current), power off (0 A current) and semi-active control seat. In the random vibration experiment, the root mean square acceleration of integrated control seat suspension has 47.7%, 33.1% and 26.5% reductions when compared with above-mentioned three kinds of seat suspension. The power spectral density comparison indicates that the integrated seat suspension will have good performance in practical application. The integrated active and semi-active seat suspension can fill energy consumption gap between active and semi-active control seat suspension.

A torsional MRE joint for a C-shaped robotic leg

Serving to improve stability and energy efficiency during locomotion, in nature, animals modulate their leg stiffness to adapt to their terrain. Now incorporated into many locomotive robot designs, such compliance control can enable disturbance rejection and improved transition between changing ground conditions. This paper presents a novel design of a variable stiffness leg utilizing a magnetorheological elastomer joint in a literal rolling spring loaded inverted pendulum (R-SLIP) morphology. Through the semi-active control of this hybrid permanent-magnet and coil design, variable stiffness is realized, offering a design which is capable of both softening and stiffening in an adaptive sort of way, with a maximum stiffness change of 48.0%. Experimental characterization first serves to assess the stiffness variation capacity of the torsional joint, and through later comparison with force testing of the leg, the linear stiffness is characterized with the R-SLIP-like behavior of the leg being demonstrated. Through the force relationships applied, a generalized relationship for determining linear stiffness based on joint rotation angle is also proposed, further aiding experimental validation.