Automated car stacker

New Zealand's first ever motorised 'car-stacker' car park was successfully commissioned earlier this year. The 30 m high vertical carousel is installed in the recently opened Bolton Hotel, which provides luxury accommodation in central Wellington.

Berill Control Systems, an Auckland company that specialises in automation and materials handling solutions, designed, installed and commissioned the control system for the automated car park. The car park itself was designed and manufactured by PowerPark Ltd.

The car stacker is a vertical carousel that can hold up to 28 cars, each parked on individual carriages. A motorised roller door on the ground level controls entry to the car park.

A 45 kW SEW motor and gearbox, controlled by a 75 kW SEW MoviDrive controller, is able to drive the carousel in either direction to deliver a car to the load/unload position in under 90 seconds.

A Siemens S7 PLC controls the car stacker, which communicates over a Profibus network to the SEW MoviDrive and the operator panel.

In designing the control system, Berill Control Systems paid particular attention to operator and public safety, whilst ensuring ease of use for the Hotel's porters who operate the car stacker 24 hours a day.

A Pilz safety relay is used for safety circuit monitoring and emergency stop shutdown. Due to the high inertia of the system, the safety relay incorporates a time delay to allow the MoviDrive to stop the motor as fast as possible under emergency stop, before being electrically isolated. The safety circuit includes a magnetically coded safety switch on the access doorway to ensure the system cannot run unless the door is closed. A switch with a removable key allows the operator to disable the system when they are parking or retrieving a car.

Photoelectric sensors are used to ensure the car is parked correctly and is not oversized. Two indicator beacons provide information to the driver to assist in parking the car.

To operate the car stacker, the porter simply types in the number of the carriage required. That carriage is automatically moved to the bottom of the carousel whereupon the car park door opens, ready for a car to be stored or retrieved.