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Posted on 08 July 2019

Sensor Module Ensures Optimum Battery Utilisation in Heavy-Duty Vehicles, called omniMoves

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Precise battery diagnostics makes maneuvering large, heavy-duty loads easier

Isabellenhütte’s shunt-based IVT Modular sensor module measures the basic battery components’ current and voltage with an error rate of less than 0.1 per cent. This exceptional degree of accuracy provides for consistent power control and efficient utilisation, especially for high-capacity battery systems. This is the reason why KUKA Roboter GmbH standardly equips their mobile platforms for heavy, difficult-to-transport loads with IVT sensor modules.

By Henning Meckel, Application & Sales Engineer Precision Measurement, Isabellenhütte

Components and manufacturing tools used to construct aircraft, wind turbines and rail vehicles can weigh up to 100 tonnes. Despite the great weight and occasionally large dimensions of these loads, workers need to be able to flexibly transport and precisely maneuver them, within a production shop for instance. In addition to crane technologies, manufacturing companies also use mobile platforms, which rank among heavy-load vehicles, for in-plant transport. These mobile platforms make it possible to transport loads that are otherwise extremely difficult to move on the ground without it becoming necessary to convert the production shops, which is the case with crane systems. The mobile platforms can also be moved with a high degree of flexibility and precision in any direction between the different working positions and workstations. This reduces the floor space required for logistical processes and guarantees more space for the production area.

KUKA’s omniMove platform design stands apart because it achieves an ideal level of maneuverability for guiding heavy loads in any direction and is able to rotate about its own axis. “With omniMove, it is possible to move heavy parts in a very small space with extreme precision – with 360-degree flexibility and positioning accuracy of ± 2 millimetres,” said Paul Wyszynski, developer at KUKA Roboter GmbH. “The omniMove’s lifting platform version means that omniMove itself can move within a range of millimetres even in a raised position, a feature useful for painting and coating aircraft, for example,” Wyszynski added. The mobile platform is also used to transport gas turbines the size of a single-family house between the individual production areas or to the test area. The freely scalable modular platform system varies in height, width and length and can be combined with other vehicles for a dual- or triple-vehicle transport configuration. This also makes it possible to transport loads such as an entire aircraft body. The system can be operated by remote control, by optical steering and guidance or completely autonomously with laser scanners.

Precisely calculated battery capacity, high utilisation rate

The omniMove’s electric drive concept is highly efficient, quiet and can operate for prolonged periods. The KoM UTV-2 E375 model, for example, has a minimum operating time of four hours. For technical and economic reasons, it is essential that a heavy-load vehicle’s available power can always be used efficiently. This is the reason why the lead-gel batteries standardly used in omniMove are equipped with current and voltage sensors based on Isabellenhütte sensor modules, which are considered the leader in shunt-based current measurement technology.

KUKA’s omniMove mobile platforms are used during aircraft construction, among other things, to transport extremely heavy loads weighing up to 100 tonnes

Informed, reliable statements about a battery’s functionality, such as its state of charge or state of health, or a battery’s state of function (namely its ability to meet certain requirements such as starting performance) are only possible if current and voltage can be calculated to an extremely accurate degree. “Based on these measurement values, the flow of energy can take place in a controlled fashion, loading times and loading cycles can be optimised and the operating life of the battery can ultimately be extended,” confirmed Jens Hartmann, Sales Director ISAscale at Isabellenhütte. The high utilisation rate of omniMove batteries is achieved thanks to the precise measurement of battery capacity.

KUKA’s vehicles feature high-capacity battery systems. The systems come standardly equipped with Isabellenhütte’s IVT Modular sensor modules, which ensure consistent power control and efficient utilisation

KUKA uses Isabellenhütte’s IVT Modular sensor module to measure current and voltage in omniMove vehicles. Isabellenhütte further developed this field-tested IVT sensor module to allow individual confi gurations with custom-selected modules. This ensures that the system can be adapted to customer requirements at short notice. “The standardisation of modular functionalities saves time during the manufacturing of sensor modules individually selected by the customer,” explained Jens Hartmann. “This has a favourable impact on development costs.”

Isabellenhütte’s shunt-based IVT Modular sensor module measures current and voltage in the battery systems of KUKA’s omni-Move platforms with an error rate of less than 0.1 percent

CAN interface proves to be a winning choice

The components that customers can select are isolation, overcurrent detection, hardware and software triggers, current measurement range, voltage measurement channels, interfaces and input voltage. With regard to input voltage, the IVT Modular can be configured to a 5-V regulated supply or to an unregulated supply voltage of 5 to 16 V or 9 to 40 V. Galvanic isolation is possible for high voltages of up to 800 V. A hardware trigger – an extra pin that makes it possible to initiate the series of measurements with an external trigger mechanism – can also be selected. An additional software trigger is part of the internal software and integrated in each module. There are five different current measurement ranges, starting from ± 100 A with a resolution of 3 mA up to ± 2.500 A at a resolution of 186 mA. The IVT Modular has three voltage measurement channels for a measurement range of up to 800 V. The three voltage inputs can be configured to monitor three other potentials in the system.

The CAN interface configuration option proved to be the main factor in the decision to use the IVT Modular in the battery system of KUKA’s mobile platforms. “Before switching to Isabellenhütte’s sensor modules, we were using sensors that had a serial interface only. That made analysing the data more costly and complex, as the units used to conduct the analysis had to be heavily adapted and customised,” according to Paul Wyszynski. Another feature of the IVT is overvoltage detection for positive and negative currents flowing while batteries are charged or discharged, for example. The software can be used to set the threshold value and a hysteresis.

“In making the decision to go with Isabellenhütte, it was also important to us that we would get a sensor that provides extremely precise measurements.” Before the IVT Modular was implemented, current measurement was conducted using Hall sensors with an accuracy of no more than one ampere. In contrast, logging measurement values with the help of Isabellenhütte’s sensor module is based on shunt technology and has the advantage that the accuracy of current and voltage measurement is extremely high across the entire potential range of temperatures and under all technical environmental conditions. The IVT’s initial measuring accuracy comes to within 0.1 per cent and 0.5 per cent across the entire temperature range. Thanks to extremely low resistance values of 5 μΩ to 285 μΩ, power loss is likewise kept to a minimum. Isabellenhütte’s shunts experience virtually no drift in the temperature range from -40° to +85° C, making them almost impervious to the effects of temperature.

In addition to the modules that can be selected, the IVT boasts other features. A bootloader makes it possible to load new firmware, which can be used to receive new functionalities. Diagnostics provide information about the sensor’s functional range, which means that while in use, the sensor logs and stores certain values, such as maximum voltage, current, temperature and operating hours, all of which can be used for statistical analyses.

Alarm sounds when low capacity detected

KUKA’s omniMove vehicles have been standardly equipped with the sensor module ever since the IVT Modular was implemented last year. The sensor module sends data on current and voltage to the central computer via the CAN interface. Every 100 milliseconds, the computer in omniMove recalculates the capacity for each battery using this data and the specific curves. With these calculations, it is possible to determine whether there is enough energy for the present task. “If not, then we take action accordingly. An alarm on the vehicle is sounded and the operator and the higher-level control system are notified,” said Paul Wyszynski.

At the same time, the collected data is analysed in a way that is specifically suited to the batteries used in omniMove since the chemical reactions inside a battery are never linear, but rather dependent on variables such as ambient temperature, how high the current drain is and the age of the battery. According to Paul Wyszynski, “For our omniMove platforms, there is one battery unit per drive, and each battery unit consists of eight large high-capacity battery trays. Unused capacities would have a major effect on our vehicles. Determining the exact flow of energy in the batteries is therefore crucial to our vehicles.”

 

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