June 2019 Design Notes

Hydraulic actuators bring the powerto the HyQReal quadruped robot

Edited by Mary C. Gannon, Editor

Researchers from Moog and IIT-Istituto Italiano di Tecnologia recently completed the design, assembly and testing of the new version of the hydraulic quadruped robot HyQ,called the HyQReal. Its capabilities were demonstrated by pullinga 3,300-kg (7,275 lb) airplane for more than 10 m (394 in). Thecompacte HyQReal is just 1.33 m (52 in.) long, and stands only 90cm (35 in.) tall and weighs 130 kg (287 lb), even with hydraulicinfrastructure and batteries onboard. The robot has customizedrubber feet for high traction on the ground and is protected byan aluminum roll cage and a skin made of Kevlar, glass fiber andplastic. A 48-V battery powers four electric motors connected tofour hydraulic pumps. The robot has two computers on board: onededicated to vision and one to its control.

The new design was tested in the Genova Airport, with the support of Piaggio Aerospace, to demonstrate the power of HyQReal by pulling a Piaggio P180 Avanti, a small passenger airplane weighing more than 3 tons, with a length of 14.4 m (567 in.) and a wingspan of 14 m (551 in.).

Moog partnered with IIT, a research institute that promotes excellence in basic and applied research fostering Italy’s economic development, in 2016, when both created the joint lab to develop the next generation of hydraulic legged robots. The partnership combines IIT’s knowledge of designing the hardware and software of legged robots, with Moog’s expertise in miniature, highperformance actuation solutions.

The HyQReal robot is developed to support humans in emergency scenarios. These hydraulically powered quadruped robots have been under development by researchers at the IIT since 2007. The long-term goal of the project is to create the hardware, software and algorithms for robust quadruped vehicles for rough terrain that can be tailored to a variety of applications, such as disaster response, agriculture, decommissioning, and inspection. Compared to the previous versions, HyQReal is completely power-autonomous with onboard hydraulics, batteries and wireless communication. Furthermore, the robot features a higher ruggedness, reliability and energy efficiency.

“Pulling a plane allowed us to demonstrate the robot’s strength, powerautonomy and the optimized design. We wanted to achieve something that has never been done before, and we succeeded last week,” said Claudio Semini, project leader at IIT’s Dynamic Legged Systems Lab.

For the HyQReal, Moog developed the majority of the hydraulic actuation system, including the hydraulic pump units, smart manifolds, fluid rotary unions and Integrated Servo Actuators (ISA). The Integrated Smart Actuator is a lightweight hydraulic actuator with integrated servovalves, control electronics, sensors and bus communications designed for mobile robotic applications. Moog has specifically developed these components for the HyQReal and will offer this technology to equipment builders in the mobile robotics market where energy efficiency and high performance are critical.

According to Burkhard Erne, manager for Growth & Innovation at Moog Inc., “Small, mobile robots typically use electromechanical motion control solutions. HyQ-Real is larger and more powerful than many other mobile robots, and it is designed to master unstructured terrain, outdoors. For high-power dexterous motion control, hydraulics has numerous advantages including: substantially lower “unsprung” mass (weight of suspension and components connected versus supported by the suspension), higher power density, better drive transparency, integral cooling and lubrication. These advantages help the robot to move faster, to walk more dynamically in unstructured terrain and to be more robust when hitting obstacles.”

IIT has led the overall development of the robot’s hardware and software. In terms of hardware, IIT focused on the design of the torso, legs, electronics, hydraulic hoses, and fall protection and sensing technology. Additionally, it coordinated the integration of the actuation subsystems developed by Moog. In terms of software, IIT adapted its locomotion control framework that it has developed over the last decade.

“Thanks to IIT and Moog’s complementary expertise, we managed to enhance our control software with increased safety and modularity,” said Victor Barasuol, who is in charge of HyQReal’s control technology.

The HyQReal team at IIT is international, composed of 14 people from Italy, Switzerland, Brazil, England, Canada, Egypt, the Netherlands, and Mexico. The development of HyQReal was funded by the Istituto Italiano di Tecnologia and Moog Inc. with the support of INAIL – the National Institute for Insurance against Accidents at Work and the European Union under the framework of project ECHORD++

To see a video of the HyQReal robot in action, find this article at fluidpowerworld.com.

Moog Inc. | moog.com/industrial

The HyQReal quadruped robot is powered by hydraulics from Moog. The company partnered with IIT-Istituto Italiano di Tecnologia in 2016, to design and now test the newest HyQ.

Hydraulic accumulator system helps new blow molding facility

Edited by Mike Santora, Associate Editor

Blow molding plant for plastic products at Roth Hydraulics USA in Watertown, N.Y.

There were significant challenges when Roth Hydraulics needed to design and install a large new blow molding plant for plastic products at its production site in Watertown, N.Y. The project connected the manufacturer’s skills in two fields — hydraulics and plastics processing. The design of the new hydraulic accumulator system now permits high-speed production, ample power reserves, and substantial energy savings.

Weighing in at 125 tons and with a clamping force of roughly 300 tons, the blow molding plant is equipped with three extruders. The production plant is also fitted with three sensor-controlled piston accumulator systems for various hydraulic functions in the production process. Roth chose this configuration because hydraulic energy is required to open and close the nozzles, to extrude the plastic tube, and for all movements that the blow molding plant undertakes. The hydraulics facilitate movement in the plates, the two-part mold, the blow pin and blow needles for letting in air, the mold closing mechanism during the blow molding process, and the control of the wall thickness of the plastic. Both halves of the mold can be moved separately, allowing them to move both in and out of synch and at different speeds. Cylinders fitted with locking devices at the four corners of each mold half regulate the clamping force. Clamping cylinders support the mold as it closes to a precise fit while withstanding blowing pressure of up to 87 psi.

Roth Hydraulics pressure vesselplant with a customer-specificscrew joint system.

The mold itself weighs 15 tons (7.5 tons per half) and can open by up to 9.84-ft at a speed of 11.8-in./sec. Each piston accumulator system has a working pressure of 2,600 psi and a maximum pressure of 3,100 psi. Proportional valves control how the two mold halves close and how the plastic tube feeds into the blow mold.

John Pezzi, V.P. Operations at Roth North America, explained, “The piston accumulator systems have allowed us to reduce the electrical load of our hydraulics by around 75%. This reduction covers the load from our pumps, motors, and heat exchangers. Cutting energy consumption to a minimum improves our environmental footprint and helps to conserve resources.”

The piston accumulators for machinery and systems come in sizes ranging from 0.026 to 396 gal. Standard systems are available with a maximum operating pressure of 5,100 psi, while customized designs can handle up to 17,500 psi with variable pre-load pressure.

Depending on their field of use, increases in capacity are possible by installing auxiliary gas bottles to be used with the piston accumulators. Even compact, large-scale systems with a total volume of well over 26,400 gal can be manufactured and supplied, ready for connection — by coupling together any number of piston accumulators and auxiliary gas bottles. The accumulator systems are suitable for use in temperatures ranging from 14 to 176 °F with versions available that can handle larger extremes: as low as –76 °F and as high as 392 °F. Roth designs fluid connections and sealing systems for the piston accumulators to order based on its customers’ requirements. It is not possible for any gas

to escape suddenly on the fluid side. With its large new blow molding plant, Roth now has five production sites located throughout the world that use blow molding processes to create plastic products. All of them are equipped with Roth Hydraulics piston accumulator systems.

Roth Hydraulics | roth-hydraulics.de

Cloud-connected assembly machinerysimplifies predictive maintenance

Edited by Mary C. Gannon, Editor

The latest generation of machines for the pre- and final assemblyof cutting rings (Type SPR-PRC-POC) and forming machines for Stauff Form(SFO-F) now come with a built-in connection to the cloud.

This offers users significant advantages — for instance with software updates. Up to now, Stauff Service had to contact the user of the machine and agree to a time at which a network connection could be established and an update installed. Or, alternatively, the software was updated in situ using a laptop with a network connection. In future this can be done online. Stauff Service simply needs to agree to a time with the user at which the machine is online and not in use.

Updating the machine for new uses will also be made easier. Stauff experts can now also relatively easily transmit new parameter sets if the user of the machine is working with different tube materials for which the requisite parameters were not supplied when the machine was delivered. This addition provides the customer with a new benefit: the machine documents online in detail the assembly processes performed and enables them to be called up online. They can then be printed out and used as evidence of correct assembly.

A further benefit also comes from the option of viewing the machine’s history and parameters via an online service. According to Dipl. Ing. Oliver Wagner, Electronics Developer at Stauff, “We can now analyze data together with the user and optimize the machine’s settings if we need to.”

One example of this is if the parameters show that the cylinder pressure in a certain process is always at the limit of a defined and stored threshold value. “We can then specifically counteract this and so maintain the quality of cutting ring installation or forming at a high level,” Wagner said. “And if the machine were to malfunction, the cause can be quickly identified, as all the relevant data for the machine as well as for the individual tools can be accessed in the cloud.”

Requisite data security is guaranteed in all the use cases presented here, as all data is exchanged encrypted with the cloud and vice versa. The data is therefore protected against unauthorized access, misuse and manipulation.

This cloud connection means that Stauff is manifesting key functions — and benefits — of predictive maintenance in its machines. This solution is achieved through the use of a built-in SIM card, which can be used in all industrial regions of the world. Existing machines can be simply and easily retrofitted with the module.

Stauff | stauff.com

Tube forming assembly machines can be easily monitored in future via a cloud connection. Software updates and new parameter sets can also be installed in this same way. Documentation and evaluation of the orders completed is also simplified by the cloud connection. Image courtesy - Walter Stauffenberg GmbH & Co. KG

Electrification exposes hydraulic-pumpshortcomings

Ken Korane, Contributing Editor

Typical forces in an axial-pistonpump can lead to issues inbattery-powered equipment.

Heightened concerns over climate changeand global warming are key reasons for thegrowing interest in zero-emission vehicles.Battery-electric mobile machines, while stillmainly in the prototype stage, may requirehydraulic-pumps and variable-speed drives to evolve tosuit future applications.

Hydraulic pumps are high-performance components. However, according to engineers at Bucher Hydraulics, Klettgau, Germany, they have some fundamental flaws that highlight a considerable need for improvement in the face of new demands.

Technically mature and well-proven hydraulic pumps and motors work to their full potential in mobile machinery, traditionally designed and engineered for use in combination with diesel engines. They were invented for such applications, have been continuously improved over decades and are suitably efficient in this combination today. Having said that, these mature solutions are clearly reaching their limits in new applications involving electrification of the drive train, particularly where battery-powered machines are concerned. This is evident in almost all the application-critical factors: from starting behavior and installation envelope to noise level and efficiency.

Battery capacity is expensive and it therefore needs to be used efficiently, but the extent to which this can be achieved depends largely on individual components in a system. Recent electrification projects clearly confirm the high efficiency of electric drives. The efficiency of hydraulic systems is lagging behind in comparison, and is not ideal for these applications. Using a simple, low-cost pump results in high power losses at the expense of the battery. Valuable battery capacity is needed just to make up for the power losses, and it is inevitably converted into useless heat.

High pulsations typicalin axial-piston pumpsresult in problematicnoise levels in electricdriveapplications.

Power losses

The efficiency of a hydraulic pump and its power losses directly affect costs and emissions. Consider the example of a pump with an 80 cc/rev displacement operating at 250 bar pressure and 1,500 rpm. Pump efficiency η p = 0.85 and power losses at the shaft = 8.8 kW.

The power lost at the hydraulic pump must also be supplied by the electric motor, which means electrical efficiency η e (e-motor + inverter) = 0.92, which equates to a power loss = 9.5 kW at the incoming electrical supply. After a running time of 1,000 hours, this equals 9,500 kWh.

Using the German Environment Agency’s CO 2 emissions factor for 2017, this gives an emission of 5,102 kg CO 2 just to make up for inherent losses resulting from inefficiencies in the motor/pump system. In addition to the increased emissions, compensating for the power loss at the hydraulic pump will, of course, also have an impact on costs: 1,000 hours @ $0.16/kWh = $1,520.

Due to their particular design, axial piston pumps generate considerable noise. The pulsating displacement of the hydraulic fluid, and the related alternating and widely fluctuating internal pump forces, result in housing vibrations that ultimately transmit to the entire machine. This causes a high noise level in the application.

Although sound insulation can be added as a secondary measure, that is always associated with extra work, the need for a larger installation space, and additional costs. In industrial settings this is sometimes unavoidable, but it is almost unthinkable in the mobile-hydraulics sector due to the limited space availability.

When hydraulic pumps are used with diesel engines as originally intended, the problems of physical pulsation are barely noticeable. This changes fundamentally in applications with quiet electric motors, where the characteristic loudness becomes prominent in an extremely disagreeable way and is completely rejected by end users. Instead, they demand the lowest possible noise emission over a wide range of speeds and pressures.

A related concern is how the pump performs at low speeds. That is because at high pressures, to prevent high wear due to mixed friction, variable-speed pumps must not fall below a certain minimum speed. This is particularly evident when positioning heavy loads, where only a low flow rate at high pressure will guarantee precise movements.

In this case, speed is an important criterion for establishing lubricating films. However, due to the minimum speed limit (not less than 1,000 rpm), the pump delivers too much oil and the excess has to be discharged via a bypass. At high pressure, this results in large losses. These losses also have to be made up for by the battery: some of its capacity is simply being converted into useless heat. Last but not least, the high pressure of 350 bar that is required in mobile machines cannot be attained with simple external gear pumps.

The situation is similarly critical when the pump operates as a motor. When energy efficiency is one of the most important issues, the overall efficiency of the hydraulic drive unit does not score highly due to its inadequate energy recovery. When recovering potential energy (for example, a raised weight) and transferring it to an energy storage device, the losses are simply too high — which ultimately means that too little energy returns to the battery.

Another negative feature that make the use of hydraulic drives more challenging is the starting behavior of hydraulic motors, especially those based on a swashplate design: the motor is initially subject to loads and static friction before it suddenly starts to move. This process presents application difficulties, and it has a damaging effect when, for example, a hoist winch is being used to jog-position an awkward load. In addition, operation at low speeds is subjected to superimposed torque pulsations. This, in turn, can lead to oscillations in susceptible machines and thus make secondary measures necessary.

Last but not least, the substantial installation space that is needed is a drawback: large, non-compensated forces in bent-axis motors can only be absorbed by extra-large ball or roller bearings. This increases the space required in the machine, so integration is less straightforward.

All in all, there is an urgent need to improve hydraulic pumps and motors in terms of their efficiency, noise generation, installation envelope and variable-speed capabilities. The demands placed on mobile machinery — which are already high — will only increase in the future.

The large, non-compensated forces in bent-axismotors need to be absorbed by extra-large ball orroller bearings. This increases space requirementsand makes integration more difficult.