The aerodynamic characteristics of centrifugal compressors are examined with special attention given to the range of flows normally in the unstable region. They are examined for the intended purpose of extending the compressor’s useful stable range. Two such means are investigated, but a close coupled aerodynamic resistance designed to achieve negative combined slope showed the greater promise. A number of experiments are performed in which the geometry and location of the close coupled control devices are varied. It is shown that with adequate design, stable operation is possible down to 40 percent of the normal surge flow. This can be done with hardware the configuration of which is practical and with attendant additional losses which are not prohibitive. The rationale and the empirical work are devoted to the single stage case but an examination is made of the stability considerations for the case of multi-stage machines.
The increased number of vehicles and poor road conditions in many countries result in slow moving traffic. At low-speeds, riding a motorcycle requires continuous input from a rider to achieve stability, which causes fatigue to the rider. Therefore, in this research, the low-speed stability of a motorcycle is studied using a theoretical and experimental approach to identify the parameters that can reduce the rider’s effort. Initially, a linear mathematical model of the motorcycle and rider system is presented; wherein, the equation of motion for the stability of the system in roll direction is derived. The open-loop and closed-loop poles from the equation are calculated to determine the regions for the low-speed stability. Subsequently, experiments are conducted on the motorcycle instrumented with the required sensors, on a straight path at speeds below 10 km/h. The input and output parameters from the experimental data are analyzed using a statistical method. Steering angle and steering torque are the input parameters; roll and yaw angles and their corresponding velocities are the output parameters selected for the analysis. Correlation and lead time between the input and output parameters are compared to identify the parameters useful for the rider to attain the low-speed stability. The results obtained from the experimental analysis validate the mathematical model. In addition, these findings also validate that the input parameters required to control the motorcycle to achieve low-speed stability can be estimated using the identified output parameters.
Motorcycles are a primary mode of daily transportation in many developing countries, especially in towns and cities. The increased traffic congestion constrains the average speed of the motorcycle, causing stability and safety concerns for the riders. A controller that assists the riders can improve this scenario. This paper presents a new controller developed using an experimental study that improves the low-speed stability of a motorcycle. The experiments were conducted on a motorcycle with the riders of three experience levels: beginner, intermediate and expert. The input parameters: steering angle and steering torque; the output parameters: roll angle, yaw angle, roll rate and yaw rate were measured. Critical input and output parameters were identified statistically from the experimental measurements and used for the controller modelled in Simulink. The controller model was co-simulated with a multi-body dynamics model of the motorcycle. The co-simulation results showed the controller developed herein stabilises the motorcycle model at low speeds.
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