Measuring dynamic parameters using a so-called inertial measuring unit (IMU), i.e. recording acceleration, speed and/or positioning has a wide range of application, e.g. in the shipping industry, military, space research or automation. In the case of the car industry, this equipment is primarily used to evaluate the driving manoeuvres of a vehicle or for recording a route in combination with GPS units. It was just this need to monitor and analyse the driving properties of vehicles (cars or motorbikes) that prompted BUT scientists to construct a mobile IMU prototype which offers several advantages over existing state-of-the-art devices.
The device structure
The IMU collects data using two sets of sensors arranged in three mutually perpendicular axes: gyroscopes measuring angular speed provide information on the orientation (turning) of a vehicle while accelerometers record vehicle acceleration. Printed boards with sensors are located on the walls of a precisely cut aluminium base.
The analogue signal from sensors is then pre-processed by an integrated microprocessor. The analogue signal is converted to a digital signal using sampling. As the processor is programmable, it allows the user to extend the application options of the device, in particular by setting different sampling frequencies.
The last part of the IMU is a data carrier on which the collected data is saved. A memory card has proved to be a practical solution, since it can be replaced easily once full. The solution also includes software for transferring data and processing them by PC.
Energy self-sufficiency and mobility
Current designs available in the market require a wire connection to a PC, which limits the IMU size and battery endurance. Most currently available IMUs are connected to the monitored object (a strap-down approach), so the small size and low weight of this device are an undisputable advantage which, in contrast to available designs, enables the IMU to be used with motorbikes as well. The newly-designed unit has its own power supply from AA batteries and is therefore designed to be completely autonomous.
The fundamental innovation of the equipment is its flexibility. The sensing part of the IMU is detachable, so the device can be used as a datalogger or a device for collecting and saving information from signals coming from another source using an attachable connector. The device is simple, low-energy and low-maintenance, and constructing it is not difficult either: a normal professional can do it using components readily available in the market.
The solution originators are employees of the BUT Institute of Machine and Industrial Design Ing. Milan Klapka, Ph.D., doc. Ing. Ivan Mazůrek, CSc. and Ing. Zbyněk Strecker. The research was supported from the funds of the research project MSM0021630518 “Simulation Modelling of Mechatronic Systems”. The IMU construction is protected as a utility model.
Title figure legend:
Snímače - Sensors, Mikroprocesor - Microprocessor, Paměť - Memory,
akcelerometry - Accelerometers, gyroskopy - Gyroscopes
