Electromagnet control device and electromagnet system

An electromagnet control device for controlling current flowing through a coil of an electromagnet, which comprises a yoke and the coil, comprising:

• an instruction value obtaining unit constructed for obtaining a magnetic flux density instruction value corresponding to a target value of a magnetic flux density that is obtained by making current flow through the coil, or obtaining information by which the magnetic flux density instruction value can be specified;
• a current value determining unit for determining, based on the magnetic flux density instruction value, a value of current that is made to flow through the coil;
• a storage unit for storing first, second, and third functions that are based on measured data of hysteresis of the electromagnet;
• and
• a driver for applying current, that has a step waveform or a ramp waveform, to the coil in accordance with the determined value of current:
• wherein
• the current value determining unit is constructed to execute
• a first process for determining, based on the first function, a value of current that is made to flow through the coil, in the case that the magnetic flux density is to be increased from that when the yoke is in a demagnetization state;
• a second process for determining, based on the second function, a value of current that is made to flow through the coil, in the case that the magnetic flux density is to be decreased from that when the yoke is in a first magnetization state;
• a third process for determining, based on the third function, a value of current that is made to flow through the coil, in the case that the magnetic flux density is to be increased from that when the yoke is in a second magnetization state;
• a fourth process for expanding or reducing the second function by use of a first scaling ratio for transforming it to a fourth function, and determining, based on the fourth function obtained after above transformation, a value of current that is made to flow through the coil, in the case that the magnetic flux density is to be decreased from that when the yoke is in a third magnetization state;
• and
• a fifth process for expanding or reducing the third function by use of a second scaling ratio for transforming it to a fifth function, and determining, based on the fifth function obtained after above transformation, a value of current that is made to flow through the coil, in the case that the magnetic flux density is to be increased from that when the yoke is in a fourth magnetization state:
• and
• the current value determining unit is constructed to
• determine, in the fourth process, the first scaling ratio in such a manner that the second function fits measured data that are obtained in advance by decreasing the magnetic flux density from that in the third magnetization state;
• and
• determine, in the fifth process, the second scaling ratio in such a manner that the third function fits measured data that are obtained in advance by increasing the magnetic flux density from that in the fourth magnetization state.