# Model-oriented design in the creation of a lifting mechanism and its drive

### Abstract

### Keywords

#### For citation:

Shestakov I.V., Safin N.R. Model-oriented design in the creation of a lifting mechanism and its drive. *Journal of «Almaz – Antey» Air and Space Defence Corporation*. 2020;(1):64-76.
https://doi.org/10.38013/2542-0542-2020-1-64-76

## Introduction

Model-oriented design (MOD) [1, 2] is an effective way of developing new products, debugging of control systems of complex and high-technology technical equipment, and also an effective tool for the performance check of systems (assemblies) that include components of different simulation domains (hydraulics, pneumatics, mechanics, thermodynamics, electromechanics, etc.). MOD allows to significantly reduce the time required for starting batch production of a product, reduce the number of prototypes and avoid major errors at the early stages of design. This paper gives an overview of experience gained during applying this method at experimental design bureau (EDB) of PJSC “Kalinin Machinery Plant, Yekaterinburg” (MZiK) by an example of developing a system (complete) model of a crane-manipulator unit (CMU) and HIL simulation of CMU operation.

## Research objective

In this paper, a crane-manipulator unit (RF patent for utility model No. 162251) shown in Figure 1 (view of geometrical model in Creo Parametric software (SW)) is the object under study. CMU consists of the following main kinematically interconnected components: base, rotary foundation, boom, jib, telescopic part and hoist.

**Fig. 1**. General view of the crane-manipulator unit: 1 - base; 2 - rotary foundation; 3 - boom; 4 - boom hydraulic cylinder; 5 - jib; 6 - jib hydraulic cylinder; 7 - telescopic part; 8 - hoist

CMU has a relatively wide field of application and the majority of such units is included in dual purpose machinery (civil and military). They can be used as [3]: transport and loading vehicles of artillery and missile systems, engineer vehicles for laying of cross-country routes and roads, construction of aerodromes, bridges and passages, equipping artillery and missile fire positions, command posts, communication posts, etc. In this paper, CMU means a military purpose traversing gear intended for series reloading of launchers (L) and launchers and loaders (LL).

The crane lifting capacity at outreach of 3,500 mm from the foundation turning axle equals to 6,350 kg (maximum 8,000 kg).

The objective of this work is to develop a virtual prototype of CMU article, model electrohydraulic drive control system, and test the system model in online mode. In the course of model-oriented design of a lifting mechanism, simulation was carried out in MATLAB SW.

## Procedure of addressing research objective

Model-oriented design of a lifting mechanism includes the following stages: development of a hydraulic part model; development of a mechanical part model; development of an electrical part model; development of a system model; synthesis of control algorithms and launch of the system model on a real-time computer.

Thus, to develop the CMU system model, an object was broken down to subsystems. In the end, the system model is represented by subsystems (virtual rigs): hydraulic part; mechanical/hydraulic mechanical part and electrical part with the control system.

Development of the hydraulic part model includes five subtasks [4]: forming of a list of circuit components, simulation of individual components, verification and modification of units models, model compilation, and simulation of basic modes. The main components of the hydraulic part are as follows: pumping plant at the inlet of hydraulic system, hydraulic motors (hoists and foundations); cylinders (booms, jibs and telescopes); valves (safety valves and nonreturn valves); distributors; main lines.

The basic parameters of CMU foundation hydraulic motor are as follows: displacement - 16 cm^{3}; rated speed - 3,000 rpm; inlet pressure

- 20 MPa. The basic parameters of CMU hoist hydraulic motor are as follows: displacement - 28 cm
^{3}; rated speed - 1,920 rpm; inlet pressure - 20 MPa

The boom hydraulic cylinder piston diameter and stroke are 140 and 562 mm. The jib hydraulic cylinder piston diameter and stroke are 200 and 545 mm. The telescope hydraulic cylinder piston diameter and stroke are 100 and 2,490 mm, respectively.

In the distribution valves (hydraulic distributors), the equivalent diameter is 20 mm and the complete opening time is 2 s.

The following figures (Fig. 2 and 3) show the examples of block diagrams being part of the CMU simulation and mathematical model.

Figure 2 shows a block diagram of the boom hydraulic cylinder.

Figure 3 shows a block diagram of the boom mechanical part. The available hydraulic and mechanical parts of CMU were designed in a similar way.

**Fig. 2**. Block diagram of boom hydraulic cylinder

**Fig. 3**. Block diagram of boom mechanical part

The subsystem models were developed to sufficient detail to allow for further study of transient processes in certain sections, which were then used for the development of the CMU system model. At the stage of model development, component ratings were used. Some of these parameters will be defined more precisely later based on in-situ testing.

Electric motor DAT 15000 is used in the electric drive of CMU hydraulic drive (pumping plant at the hydraulic system inlet of the crane-manipulator unit) and is controlled by a power controller - KS-220 with the use of application software (Certificate of State Registration of PC Program No. 2016617322). Selection of an electric motor for operation as part of the variable speed drive is a very important factor having influence on the reliability of operation of the drive/ working mechanism and the whole article. A novel traction electric motor DAT 15000 is used in this project (RF patent for utility model No. 184734). The parameters of DAT 15000 equivalent-T are given in [5]. The electric motor is designed for operation with the power supply (among other options) from frequency converters (FC) and for use in severe operating conditions under the influence of various negative factors. To increase reliability of the electric motor, its design also includes a cooling circuit that consists of cooling channels axially passing through the rotor. The adopted solutions allow to improve the internal air circulation and thus enhance the heat transfer circuit.

Based on studies [5, 6], the principle of scalar frequency control is implemented in the control system of an asynchronous variable-frequency electric drive (AVFD). In the scalar control system of DAT 15000, the main controlled variables of electric drive state are the modulus of stator winding terminal voltage vector (U_{sy}*) and the angular frequency (ω_{s}*) of this vector rotation relative to the stator.

Based on the results of simulation [5] and spectral analysis [6] at DAT 15000 power supply from FC (power controller KS-220) with frequencies of pulse width modulation (PWM) of 1, 2, 4 and 8 kHz obtained using Powergui - FFT Analysis tool (FFT - Fast Fourier Transform), the optimum frequencies (with regard to the minimum coefficients of higher-harmonic voltages and stator current) are those with PWM *f*_{ШИМ} = 4 and 8 kHz. At that, it should be taken into account that due to an increase of the switching frequency, switching losses in an autonomous voltage inverter are proportionally increased and its allowable effective power is reduced. Hence in this project, for this electrohydraulic drive of CMU, it is assumed that the optimum PWM frequency at DAT 15000 power supply from KS-220 is *f*_{ШИМ} = 4 kHz.

As stated above, the detail model of the electric drive for CMU hydraulic drive control is specified in paper [5]. In DAT 15000 control system, stator current cut-off is used (I_{smax} = 2I_{ном}) to ensure effective current limitation in transient modes of start, braking and changing of electric motor shaft load, including locking.

Figure 4 shows Simulink model of electrohydraulic drive, where the system of scalar frequency control is implemented.

In the end, the CMU system model was compiled of the subsystem models to check their functioning and interaction (a check for compliance with the requirements of the statement of work - SOW), as well as to debug the control algorithms. A general view of the system model is shown in Figure 5.

Two types of control can be implemented in the CMU system model: open and closed. An open type of control consists in the issuance of commands in the predefined order and in given time intervals, i. e. optimization of a conventional cyclogram. To assign commands, Signal Builder block is used.

A conventional cyclogram of open-type control system is shown in Figure 6. The following is marked on the same: Boom; Jib; Hoist;

Foundation; Telescope; Cargo; Pump_pwr - pumping plant. The conventional cyclogram of operation includes the following: boom lifting; jib lifting; extension of telescope; lowering of hoist rope; engagement of cargo; lifting of hoist rope; rotation of foundation; lowering of hoist rope; disengagement of cargo; lifting of hoist rope; rotation of foundation to its initial position; retraction of telescope; lowering of jib and boom.

To implement closed type of control, the finite state automaton method based on Stateflow module was selected. The control system with feedback relies on the information from end probes, presumably arranged on all CMJJ items.

The general view of the closed-type control system is shown in Figure 7. The following is marked on the same: IDLE - idle speed; Boom_UP - lifting of boom; Jib_UP - lifting of jib; Telescope_UP - extension of telescope; Hoist_DOWN - lowering of hoist rope (repeated twice); Cargo_LOADlNG - engagement of cargo; Hoist_UP - lifting of hoist rope (repeated twice); Foundation_LEFT - rotation of foundation to the left; Cargo_RELEASE - lowering (disengagement) of cargo; Foundation_RIGHT - rotation of foundation to the right; Telescope_DOWN - retraction of telescope; Jib_ DOWN - lowering of jib; Boom_DOWN - lowering of boom.

**Fig. 4**. Block diagram of CMU electrohydraulic drive

**Fig. 5**. CMU system model for machine-time simulation

**Fig. 6**. Cyclogram of open control system

**Fig. 7**. Cyclogram of closed control system

As a result, usage of the finite state automaton method implemented through Stateflow module allows to use standard algorithmic patterns, such as branches and cycles, in the control algorithm and try out emergency situations (for example, failure to fulfil commands within the specified time).

Figure 8 shows a 3D model of CMU imported to MATLAB package. The crane operates as per the conventional cyclogram (Fig. 7) with cargo weight of 8,000 kg. The model includes the main crane parts taking into account their weight and dimensions, and it is based on STL files assembly (Creo Parametric).

Figure 9 shows an example of curves of pressure variation at the inlet and outlet of the hoist hydraulic motor. The curve of pressure variation corresponds to the above data (the maximum pressure rating at the hydraulic motor inlet - 20 MPa).

Figure 10 shows the output parameters of the CMU system model operation with respect to speed and travels of certain units in machine time. In particular: S_{1}, Boom, m - rod travel in the boom cylinder, m; S_{2}, Jib, m - rod travel in the jib cylinder, m; V_{1}, Hoist - rotation speed, rad/s - speed of hoist rope reeling on the cable drum, rad/s; S_{3}, Hoist - coordinate, m - travel of hoist rope (lowering/lifting), m; V_{2}, Hoist - speed, m/min - hoist rope lowering speed, m/ min; F, Foundation, deg - foundation rotation angle, °; S_{4}, Telescope, m - rod travel in the telescope cylinder, m.

**Fig. 8**. CMU simulation in MATLAB (from left to right / from top to bottom): front view; right-side view; top view; isometric view

**Fig. 9**. The curve of pressure variation at the inlet (P_B) and outlet (P_A) of the hoist hydraulic motor

**Fig. 10**. Output parameters of CMU system model (in machine time)

Based on the results of CMU operation simulation, the speed of cargo lifting/lowering amounts to 3.4 m/min on average, which corresponds to the requirements of the statement of work for the design of the CMU end product.

The developed CMU system model may be considered a virtual prototype of the real article. The structure of the system model is relatively complex, which is basically explained by the fact that each block subsystem includes its own internal blocks containing their own blocks and elements inside, and so on, to the maximum possible degree of detail and considering the required factors. It can be used both for virtual experiments, related to functioning of the article itself, i.e. for building characteristics, studying dynamic modes, specifying ratings, and for further developments. Simultaneously, the control program of an asynchronous variable-frequency electric drive KS-220 can be fine-tuned (with respect to the adjustment of: acceleration amount, output voltage frequency, frequency of PWM and current limitation). It should be noted that the current CMU system model is developed with no regard for environmental conditions (temperature, wind speed, etc.).

In the future, system model testing in online mode will be implemented. For this purpose, a semi-realistic simulation (SRS) complex “RITM” and modules of MATLAB package were used: Simulink Real-Time, MATLAB Coder and Simulink Coder.

The specialized input/output modules installed in the real-time machine - SRS “RITM”, allow to connect to external interfaces, such as analogue and digital inputs and outputs, PWM, and to work with industrial protocols, such as MIL-STD-1553, real-time UDP, RS232/RS422/RS485, etc.

Real-time models allow to approach the transition from simulation to full-scale specimens of the article, i. е., proceed to semi-realistic simulation. In the international engineering practices, the scenarios of semi-realistic simulation include, but are not limited to:

- fast prototyping of control algorithms - automatic control systems (ACS), as a tangible object model;
- Hardware-in-the-Loop simulation - HIL - the ACS is real, the object is represented by a model.

In this project, the system model was used for HIL simulation (HIL-testing) of the object. At computer simulation, real-time operation means fulfilment of two main conditions: each calculation step begins at a strictly defined time; each step of model calculation takes no more than the specified time. In practice, these conditions mean that the model calculation time is equal to the simulated process duration (to the accuracy of a calculation step).

Figure 11 shows the optimized (simplifications are implemented, among other things the finite state automaton module is excluded) system model of CMU for real-time operation. HIL-testing was performed for the control unit (power controller KS-220) connected to the semi-realistic simulation (SRS) complex “RITM”. The appearance of the semi-realistic simulation rig is shown in Figure 12, including a PC, a semi-realistic simulation complex (real-time machine), a prototype of power controller and an additional monitor.

To ensure power controller and PC communication, RS-232 adapter is used. The power controller is supplied from the lab power source. Power controller and semi-realistic simulation complex communication is implemented as follows:

- terminal board (analogue-to-digital module and its wires) connecting power controller KS-220 driver IGBT board with SRS;
- terminal board (analogue-to-digital module and its wires) connecting power controller KS-220 current sensor board with SRS.

For data exchange, PC and SRS are connected by an Ethernet-cable.

Electric motor stator currents are transferred from the system model to KS-220 via SRS terminal board. PWM signals are transferred from the system model to KS-220 via SRS terminal board.

Figure 13 shows output parameters of the CMU system model operation with respect to speed and travels of certain units in real time. Apart from the output parameters shown as in

Figure 10, the curve is supplemented with V_{3}, Foundation, rpm - foundation rotation speed, rpm.

Figure 14 shows a curve of electric motor rotation speed variation during operation as part of CMU electrohydraulic drive, obtained in real-time mode. During testing of power controller KS-22, rate of output voltage frequency variation was set by default to 10 Hz/s.

**Fig. 11**. CMU system model for real-time simulation

**Fig. 12**. Appearance of a semi-realistic simulation rig

**Fig. 13**. Output parameters of CMU system model (in real time)

**Fig. 14**. The curve of electric motor rotation speed variation, rad/s

The curve of electric motor rotation speed variation corresponds to optimization as per the conventional cyclogram (Fig. 6) and the rated rotor rotation speed of 611.42 rad/s.

## Interpretation of findings and perspectives

The real-time CMU system model allowed to optimize the control program of power controller KS-220 for electric motor DAT 15000 in the absence of the corresponding test rigs at the initial stage, which also had a positive impact on the efficiency of experimental and design efforts in general.

During development of the system model, challenges associated with the absence of sufficient initial data were addressed, interaction and information exchange with third-party organizations took place, and several model subsystems were optimized for calculation speed standardization.

At the next stage of system simulation of the lifting mechanism, the possibility of importing 3D model assemblies directly from Creo Parametric to MATLAB was implemented (Simscape Multibody Link plugin was installed), which as a result allowed for the following:

- automatic building of a detailed complete model of mechanics from the blocks (from Simulink/ Simscape Multibody library) in Simulink model window;
- assembly in the sequence similar to the model tree in Creo Parametric;
- rendering of dimensions, colours;
- rendering of connections, coordinate systems, limitations, and hinged connections;
- rendering of masses, mass centres, and inertia moments.

Besides, during import to MATLAB, a Data- File.m file with initial parameters (geometty, masses, etc.) is created automatically, which allows to introduce changes to the model when necessary and analyse any output data.

## Conclusion

In the course of work, virtual rigs of CMU parts were built, as well as a complete system model of the object. A semi-realistic simulation rig was developed based on SRS “RITM’. The CMU system model in MATLAB package allows to study the characteristics and transient processes of a hydraulic drive (pressure, consumption); the characteristics and transient processes of mechanical part (travel trajectories, reactions in the hinges, cargo lifting speed, loading torque from the hoist); the electromagnetic characteristics and transient processes of an electric drive (power controller and asynchronous motor), optimize the KS-220 control program, etc.

The obtained results allow to select optimum parameters for the assemblies and elements and to analyse CMU operation in different conditions (including emergencies). Namely:

- crane behaviour during operation with small- and large-weight cargoes;
- crane behaviour during hydraulic drive electric motor speed adjustment;
- crane behaviour during operation of one/ two pumps of a hydraulic drive;
- crane behaviour during varying of its operation cyclogram;
- variation of crane dimensions;
- variation of boom, jib and telescope cylinder volume;
- variation of KS-220 SW with respect to acceleration amount and output voltage frequency;
- variation of hydraulic drive pumps volume;
- variation of hydraulic motor displacement;
- variation of hydraulic fluid density;
- and other variations of crane parameters and operation modes.

Currently, model-oriented design is actively implemented during the development of new products at EDB of MZiK, PJSC.

## References

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### About the Authors

**I. V. Shestakov**Shestakov Igor Vladimirovich – Deputy Chief Designer for Science and Innovation of the Experimental Design Bureau

Research interests: theory of management of knowledge-intensive business processes, simulation, dynamics and strength of structures, adjustable electric drive.

**N. R. Safin**Safin Nail Ramazanovich – Cand. Sci. (Engineering), Leading Design Engineer of the Bureau of Calculations and Computer Simulation of the Experimental Design Bureau

Research interests: simulation, dynamics, and strength of structures, adjustable electric drive.

### Review

#### For citation:

Shestakov I.V., Safin N.R. Model-oriented design in the creation of a lifting mechanism and its drive. *Journal of «Almaz – Antey» Air and Space Defence Corporation*. 2020;(1):64-76.
https://doi.org/10.38013/2542-0542-2020-1-64-76