Today, a wide range of sectors can benefit from auto­mated guided vehi­cles (AGV) from online retail to manu­fac­turing indus­tries such as auto­mo­tive produc­tion and also hospital logis­tics. In an increasing number of compa­nies, they are used flex­ibly and effi­ciently for their own logis­tics because they can be designed for trans­porting a wide range of goods with different weights and spec­i­fi­ca­tions.

With the Agro­Drive, ebm-papst has devel­oped the right driving steering system, including the wheel, for this purpose (Fig. 1). In Light, Stan­dard and Heavy versions, it can move loads of up to 100 kg, 300 kg, or 500 kg per drive unit. In the maximum expan­sion stage with four driving steering systems in the Heavy version, a load capacity of two tons is possible without prob­lems. The instal­la­tion dimen­sions and the elec­trical, mechan­ical and control inter­faces are iden­tical in all versions; the impeller diam­e­ters, the speed and the accel­er­a­tion vary and also differ in the possible load capacity and the ground clear­ance.

Used in a wide range of sectors

“Each drive unit consists of two brush­less DC motors, trans­mis­sion, sensors and all the neces­sary connec­tion plugs. With the super­po­si­tion gear, the two motors contribute towards steering, accel­er­a­tion, move­ment and braking, depending on require­ments. The infi­nite steering angle enables omni­di­rec­tional move­ment of the vehicle, even from a stationary posi­tion,” explains Patrick Schu­macher, Director of Product Manage­ment Divi­sion IDT at ebm-papst St. Georgen. Due to these prop­er­ties, omni­di­rec­tional drive systems have already devel­oped a number of areas of appli­ca­tion. In auto­mo­tive produc­tion, they are used for vehi­cles for trans­porting shop­ping baskets or even bodyshells.

“The safety of the driving steering system has been very impor­tant to us right from the start.”

Henry Sämisch, Appli­ca­tion Engi­neer Divi­sion Indus­trial Drive Tech­nology at ebm-papst St. Georgen

They are the driving force behind trans­port tasks in online retail and, in the health care sector, they relieve hospital staff, e.g. when trans­porting mobile X-ray systems. They are also used by manu­fac­turers. Henry Sämisch, Appli­ca­tion Engi­neer for Indus­trial Drive Tech­nology at ebm-papst St. Georgen, adds: “In motor produc­tion in Mulfingen, the EDDY auto­mated guided vehicle with our driving steering system for trans­porting parts between the work­sta­tions provides greater flex­i­bility in the existing produc­tion envi­ron­ment (Fig. 4).”

Figure 2: The infi­nite steering angle enables omni­di­rec­tional move­ment of the vehicle, even from a stationary posi­tion. (Image | ebm-papst)

Figure 3: In motor produc­tion at ebm-papst in Mulfingen, the EDDY auto­mated guided vehicle with the ArgoDrive driving steering system for trans­porting parts between the work­sta­tions provides greater flex­i­bility in the existing produc­tion envi­ron­ment. (Image | ebm-papst)

Safety concept with func­tion modules for Siemens control systems

It is easy for the vehicle manu­fac­turer to inte­grate the ArgoDrive driving steering systems in his vehicle, not only mechan­i­cally, but also in terms of control tech­nology. “Safety concept and cabling are completely iden­tical for all ArgoDrive vari­ants,” says Patrick Schu­macher. “All-in-one-cable and indus­trial-compliant connec­tors make elec­trical connec­tion easier”. Henry Sämisch adds: “The safety of the system was also very impor­tant to us right from the start. For safety certi­fi­ca­tions, we offer all rele­vant safety indi­ca­tors such as MTTFd values, BP-10 values and the require­ments of the AGV stan­dards ISO 13849 and ISO 3691-4 are met.”

Anyone now using the S7 1500F as the vehicle control and SIMOVE for navi­ga­tion and fleet manage­ment in the devel­op­ment of an auto­mated guided system has it partic­u­larly easy. Prede­fined ArgoDrive func­tion modules make it easier to inte­grate the driving steering systems into the control program; the control of the motors then takes over the PDC600F controllers from Siemens, which commu­ni­cate with the higher control via Profinet and Profisafe (Fig. 4). “This means that a wide range of safety func­tions are avail­able for safe oper­a­tion of auto­mated guided vehi­cles and no other compo­nents are required for a func­tioning setup of the driving steering system,” adds Patrick Schu­macher.

Rule out colli­sion risks

Safety is a key issue when oper­ating auto­mated guided systems. If the working envi­ron­ment of personnel over­laps with the routes of the AGV, colli­sion risks must be ruled out. ArgoDrive offers several options for this. If the protec­tive zone is breached, for example, the drive system must give the safety control system the command for a safe stop. Above all, a high level of brake power must be avail­able for the drives. Here, the ArgoDrive achieves a delay of up to 2.5 m/s² using the elec­tric motor brakes, and imme­diate emer­gency braking is also possible using the addi­tional inte­grated brake. In order to prevent uncon­trolled move­ments, the drive unit also comes to a safe stop if the AGV power supply fails. This means that the ArgoDrive supports all typical and neces­sary safety require­ments.

up to 2,5 m/s² decel­er­a­tion

For this purpose, the indi­vidual driving steering system is actu­ated by two external controllers. The signals for the steering angle are also redun­dant and the posi­tion can be queried at any time. The STO func­tion (Safe Torque Off) inte­grated into the controllers ensures a safe stop (PLe). Holding brake and STO can also be trig­gered together. In addi­tion, the drive moni­tors that a certain maximum speed is not exceeded (SLS, Safe Limited Speed) and the vehicle only moves in the permitted direc­tion (SDI, Safe Direc­tion). The motors have two inde­pen­dent encoder systems as stan­dard: the inte­grated hall sensors for commu­ta­tion and a high-reso­lu­tion incre­mental coder for control. By comparing both signals, the elec­tronics can reli­ably record the speed in a func­tional manner.

Other safety func­tions

Added to this are other safety func­tions: SP (Safe Posi­tion) moni­tors start-up. The inte­grated steering angle encoder can also be used to monitor the posi­tion of the vehicle by comparing the signals from the motor controllers to the steering angle encoder. SSM (Save Speed Moni­toring) can also be used to ensure that the speed moves in a defined corridor. If the limit value is exceeded, the vehicle then goes into a safe state, i.e. stops. The acti­va­tion of the braking process is also moni­tored; the func­tion SBC (Safe Break Control) is also avail­able for this.

The ArgoDrive there­fore provides a safe, flex­ible and easy-to-inte­grate drive solu­tion for auto­mated guided vehi­cles, which does not compro­mise in terms of omni­di­rec­tional move­ment and compact­ness and is suit­able for use in a wide range of indus­tries. The special­ists at ebm-papst are also happy to provide support with their exper­tise when selecting and commis­sioning.