Motion control unit
When selecting a drive motor for HullBUG, consider a number of key design constraints and adjustments. Therefore, SeaRobotics chose to make two basic models, one for the wheel and the other for the track. In determining the size of the motor, parameters such as power, speed and torque of the finished part must be considered. In addition, consider the resistance of the spatula tool when moving the hull, the fluid resistance of the robot when moving in the water, the friction loss of the shaft seal that prevents the motor from being corroded by seawater, and (depending on the specific version) also consider the wheel or track. friction.
“After extensive inspections, we decided to use maxonmotor's motors and gearboxes,” Holappa said. “Maxon's motors not only provide a cost-effective solution, but are also extremely efficient and easy to install.” The company chose an EC disc motor with a planetary gearbox. The crawler version of HullBUG uses two drives (EC45flat+GP42C), while the wheeled version uses four drives.
Another EC45 motor is integrated into the robot's spatula tool. This motor is combined with a simplified helical gearbox. The vacuum system drive that adsorbs the HullBUG to the bottom of the hull uses a powerful EC90 disc motor.
Maxonmotor offers a range of DC motors with ironless rotors and brushless motors from 6mm to 90mm with power from 30mW to 500W. “The complete range of products and the high quality of service make us convinced that we have chosen the right partner,” adds Holappa. The motor manufactured by maxonmotor has a long service life and a small size. The full range of brushless EC motors are electronically commutated. This solution provides an extremely long service life because it does not cause wear. The motors selected are especially designed for robotic applications, and their specifications and weight are the core criteria for selection. The EC45 disc motor selected by HullBUG works extremely efficiently and weighs only 75 grams. All 6 EC disc motors have an output power of more than 30 watts. Torque is the most critical parameter for this application. Even in harsh environmental conditions where HullBug can be used, the EC45 can continue to deliver up to 56 megatons of ultimate torque depending on the windings selected. Holappa explains: "The huge load capacity of the GP42 gearbox allows the wheels to be mounted directly to the shaft of the gearbox, thereby greatly reducing the overall structural complexity of the system."
Gearboxes made by maxon can be matched to different reduction ratios to achieve deceleration or torque doubling depending on the application. Since the HullBUG robot car has to be fully autonomous, the design must be able to operate in battery mode for many hours. The cable only causes trouble for the spatula operation. In order to reach the end of the battery life, the scraping operation of the bio-adhesive layer must be as efficient as possible.
