public void setStorageUnit(StorageUnit storageUnit) {
		if (this.storageUnit == storageUnit) return;
		if (this.storageUnit != null) {
			this.storageUnit.removeTray(this);
		}
		this.storageUnit = storageUnit;
		if (this.storageUnit != null) {
			this.storageUnit.addTray(this);
		}
	}