Florian Verbelen

Energy efficiency measurement procedure for gearboxes in their entire operating range

Over the last decade, forced regulations and a growing social awareness with respect to energy efficiency have resulted in a renewed interest in the research for high efficient electrical machines. When an electrical motor is coupled to a machine, in many cases a gearbox or belt transmission is used. Research shows a lack of information on energy efficiency of these components. In comparison to electrical motors and drives, there is very few regulation and if efficiency values can be found in catalogues, there is no regulated test procedure available to validate the data. As a result, the reliability of these efficiency values is unknown and comparison between manufacturers and technologies is impossible. In this paper a test bench is proposed to measure the energy efficiency of a gearbox with an accuracy up to 0.4%. The test bench is used to measure the efficiency of gearboxes in their entire speed and torque range. Contour maps are used to visualize these measurement results. Moreover, a measurement campaign using different gearboxes is carried out to compare the energy efficiency in the manufacturers catalogue and the measured efficiency.

The Use of Orbitals and Full Spectra to Identify Misalignment

In this paper a “SpectraQuest” demonstrator is used to introduce misalignment in a rotating set-up. The vibrations caused by misalignment are measured by two accelerometers on the bearings and two eddy-current probes on the shaft itself. A comparison is made between the classical spectral analysis, orbitals and full spectra. Orbitals are used to explain the physical interpretation of the vibration caused by misalignment. Full spectra allow to distinguish imbalance from misalignment by looking at the forward and reversed phenomena. This analysis is done for different kinds of misalignment, couplings and combined machinery faults.

Robust sensorless load angle control for stepping motors

In industry, the bulk of the stepping motors is driven in open loop full-step mode with maximum current to avoid step loss. This results in noisy operation due to torque ripples and a poor energy-efficiency. To tackle these problems the current current level at which the stepping motor is driven can be reduced to an optimal level. In this paper, a sensorless load angle controller is proposed and implemented to optimise the drive current level. However, reducing the current level results in a diminished torque margin for load disturbances. In this paper, a countermeasure to enhance the robustness of the sensorless load angle controller against torque disturbances is proposed and assessed trough measurements.

Torque ripples in stepping motor driven systems

Stepping motor operation is characterized by torque ripples. In this paper it is shown these torque ripples are caused by both the stepping motor drive algorithms and the toothed construction of rotor and stator of the studied hybrid stepping motors. These torque ripples are analyzed, discussed and measured. The torque ripples are measured in the complete operating range of the motor and depicted in this paper for full- half- and micro-stepping. By doing this, the paper provides insight in the vibrating behavior of a stepping motor driven system and possible solutions to overcome this are placed in the right perspective.

Detection of Coupling Misalignment by Extended Orbits

In this paper a ‘SpectraQuest’ demonstrator is used to introduce misalignment into a rotating machinery set-up. Depending on the coupling used in the set-up, angular and/or parallel misalignment can be brought in the rotating system. Traditionally, the data captured by accelerometers is transferred into the frequency domain in order to interpret the vibrations measured by the accelerometers. The frequency domain has proven its usefulness but even the time domain can come in handy to draw the right conclusions regarding to misalignment in a rotating set-up. Orbit plots display the integrated data captured by accelerometers, in order to display the movement of the rotating shaft. The influence of the misalignment and imbalance on these orbits will be discussed.

Realtime locomotion control of a snakeboard robot based on a novel model, enabling better physical insights

Abstract The snakeboard is a fascinating variation of the well-known classic skateboard, and a nonholonomic structure. Therefore, a snakeboard robot is appealing for usage in control engineering education. The propulsion, which relies on cyclic movements, resembles that of many biological creatures. Hence, the challenging snakeboard modelling and motion planning received much attention in literature during the last decades. Despite all these research efforts, there is no model available in which there is a clear link between the mathematical descriptions and physical phenomena. The lack of physical insights hampers the development of a closed-loop real-time trajectory controller which is apparent by the lack of literature on such algorithms for snakeboards. In this paper, the traditional models are rewritten to obtain a model with a clear link to physical phenomena. Based on this model a closed loop controller is designed. Moreover, this rewritten model delivers the insights on actuation efficiency which are used to adapt desired trajectories a priori to more energy-efficient forms. Finally, the control and trajectory optimisation is validated by measurements on a snakeboard robot.

Modeling of a power sharing transmission in a wave energy converter

The fluctuating behavior of wave energy is a challenge to reach high efficiencies of implemented power take-off (PTO) systems due to the bidirectional movement and high variable loads. The described PTO based on a power sharing transmission (PST) tackles this by converting the bidirectional rotation into a unidirectional rotation of a generator equipped with a flywheel to reduce fluctuation in the output. The generator can then be operated at or close to its optimum efficiency. An auxiliary machine is in charge of the controls. The PST is modeled and implemented in an existing hydrodynamic model of a heaving buoy. A basic control is realised in the simulation resulting in the confirmation of the conversion to a unidirectional rotation and facilitating assessment of the machine efficiencies.

A general model for 6 switch voltage source inverter

In literature three phase voltage source inverter models are based on one specific application considering only a limited number of switching state combinations and assuming certain load properties. This paper suggests a model considering all practical switching state combinations. Time dependent load behavior is also included in the model.