The institute of Fluid Power Transmission and Control mainly engages in teaching and researching in the field of fluid transmission and control, which is a comprehensive team consisting of special knowledge from many subjects. It has 32 staff members now, among whom 10 are professors (7 of them are doctoral superiors), 8 associate professors, 2 senior engineers, 7 lecturers, and 4 engineers, 20 of whom have a Doctor’s degree in engineering.
        Its scientific work covers the theory of fluid transmission and control, hydraulic units, hydraulic control systems, system analysis and simulation, pneumatic techniques, etc. Compared with other institutes in the same field, our institute covers a wider range of research directions and reaches a higher research level. In recent years, other research directions such as computer integrated control, pneumatic bionic techniques, and functional fluid application have been added, which lead the development of these areas in China.
        Our institute has completed more than 150 national, national defense, and provincial major scientific projects, among which one was a National Natural Science Foundation (NNSF) key program, twelve NNSF general program projects, four “921 Program” projects, two National High-tech Research and Development Program of China projects, seven national high and new technological projects, eight projects of the State Commission of Science, and 1 project of National Technology Research and Development Program. Researching funds exceed 200 million RMB. We have published over 1000 research papers, over 300 of which were indexed by SCI or EI and we have applied for invention patents for over 100 items, over 50 of which have obtained the invention patents. We won the honor of “Science and Technology Advancement Second Prize”, “National Science and Technology Congress Significant Achievement Second Prize” twice and provincial and ministry prize three times.

Research Activities of Prof. Jihai Jiang’s Workshop

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    1    High Rotating Speed Hydraulic Cylinder

    The high rotating speed hydraulic cylinder is used for a hydraulic power chuck in a computer numerical control machine. It is also used for transferring power from fixed components to rotating components in hydraulic systems.
        High rotating speed hydraulic cylinder is composed of a self-balanced hydraulic slipring and a hydraulic cylinder. Plane, deep circular groove and fleet circular groove oil film face seal technologies are applied at the gap of the hydraulic slipring.
        Face seal is a kind of radial face seal. It is also called a mechanical face seal, mechanical seal for short. It is one of the main types of seal for sealing rotating axis in a liquid machine. It is mainly used as an axial seal. Compared to the soft wadding seal, the face seal has some advantages, such as low leakage, low friction, long life, stable running and simple maintenance.
        When used on the computer numerical control machine, the oil is transferred from the tank into the cavity
of the rotating hydraulic cylinder to pull or push the piston rod. The rod drives the wedge block which drives the claws to function the loosening and clamping of the work pieces. In the working process, the speed of the rotating hydraulic cylinder can be up to 7000 rpm or more. The power loss and leakage are low.
This work has been supported by NNSF two times, and we have applied two Chinese invention patents.

    2 HydraulicTransformer

        Hydraulic transformer is a unit which can transform the pressure in a hydraulic system. It can transform the pressure of a constant pressure system (CPS) to the load pressure without throttling losses. The research is to resolve the key technological problem of driving a linear load without throttling losses under CPS. The CPS with hydraulic transformer is mainly applied in the work conditions to drive a linear load such as excavators, hydraulic oil pumping units and other engineered machinery. Energy saving and environmental protection are the main advantages.
        Its key techniques includes: 1) the working principle of a hydraulic transformer; 2) new structure of the hydraulic transformer; 3) an accurate control technology for the hydraulic transformer; 4) maximum recuperative energy recovery and reuse technology for a hydraulic transformer driving a linear load. 

    3    Parallel Hydraulic Hybrid Power System

Fig. 4:  Configuration of PHHV

Fig. 5: Test on drum tester

        There are five working modes as follows: 1) Purely hydraulic driven mode: it is used to assist the vehicle with its start or to start the engine. 2) Compound driven mode: applicable to the city working cycle in which the engine works in constant speed mode and the pump adjusts the engine load to its highly effective area. 3) Parallel driven mode: applicable to the vehicles medium and low speed mutation condition when the pump rotates freely and hydraulic motor releases the energy stored in hydraulic accumulator and sends out power. 4) Engine directly driven mode: applicable to the vehicle high speed condition when the pump rotates freely and hydraulic motor is braked and its output port is sealed, while the engine drives the wheels directly through the planetary outside ring gear. 5) Regeneration braking mode: hydraulic pump is driven by outside load and stores the braking energy into the hydraulic accumulator and thus achieves the regeneration braking.
      This work is supported by NNSF, State Commission of Science and State Key Lab Opening Fund.

    5 Direct Drive Volume Control Electro-Hydraulic Servo System

        Direct drive volume control electro-hydraulic servo system (DDVC) is a combination of AC servo technique and hydraulic technique and it is a great technical production in the hydraulic field. This kind of system has the advantages of an AC motor control’s flexibility and great hydraulic force.
In DDVC electro-hydraulic servo system, variable displacement pump and proportional valve are replaced by an AC servo motor and bidirectional fixed pump. Changing the rotating direction, rotating speed and runtime of the AC servo motor can control the moving direction, velocity and position of the hydraulic actuator (cylinder or motor). The DDVC electro-hydraulic servo system is discarded in pumping stations and pipelines; it has fewer control components, high energy efficiency, more compact structure, higher reliability and controllability when compared with traditional hydraulic systems.
        DDVC electro-hydraulic servo system possesses many advantages such as smaller bulk, simpler construction, energy saving, being prone to control with computer and some others, so the system is considered as one of the most important developing directions in the field of hydraulic-control. DDVC electro-hydraulic servo system has wide range of applications. Now it has been applied to accurate forging machine, injection molding machine, shock absorbing of shipping rudder, printing machine, six DOF flat roof and some other machines. Financial benefits have already been achieved.
This work has been supported by National Defense Basic Research Program and obtained four Chinese invention patents.

    6 Research of Axial Piston Pump/motor

The axial piston pump/motor can directly connect to constant pressure network without throttling loss, so it can obtain less energy loss. At the same time, it can connect to several loads in parallel mode, there are no interference conditions among them, by the way of varying the displacement of the pump/motor to adapt to the variation of the load, we can achieve control functions. The axial piston pump/motor can rotate in two directions. It can not only work as the pump but also as the motor, and create the condition for energy recovery and re-utilization.

    The key techniques include: 1) rational design of valve, abandoning the structure of an insert, adopt high integration valve; 2) adoption of advanced valve plate technology, improvement of the PV value of the material.
We are working on: 1) optimizing the structure and decreasing the volume of the valve; 2) ameliorate the structure of the valve plate, improving processing technology, absorbing vibration and noise.
This work is supported by NNSF and State Key Lab Opening Fund, and we have applied one Chinese invention patent.

    7    Large Torque Continuous Rotary Electro-hydraulic Servo Motor

        Large torque continuous rotary electro-hydraulic servo motor is a hydraulic component used in driving the frame of a simulator which is needed to rotate continuously.
Large torque continuous rotary electro-hydraulic servo motor consists of stator, rotor, vane, pressed mechanism adopted reducing valve and pre-compressed spring. This servomotor has eliminated non-pulsation of rotating speed, flow and theoretic output torque, through friction orthogonal experimentation, materials of the friction pairs are confirmed which decrease the influence of friction to the low speed performance. Continuous rotary electro-hydraulic servo motor adopts the end oil distributing with valve plate and cover integrative structure and special vane structure, and the shape and dimension of buffer groove is designed which realize the smooth exchange between high-pressure chamber and low pressure access, and reducing the low-speed pulsation.
        Hydraulic simulators which are only driven by electro-hydraulic servo motors can avoid lower system stiff- ness, higher nonlinearity and lower control accuracy caused by a transmission mechanism of the indirect drive, and it can meet the demand of simulator performance and broaden the scope of application of a hydraulic simulator.
        When the motor is used in a driving simulator, the vane keeps closely to the inner surface of the stator under vane root’s spring pressure forming the pressure sealed capacity before starting; after starting, the oil through the servo valve from pump flows over the inlet 1. 2. The high pressure oil fluid into sealed capacity and put on the blade to produce the torque which can drive the rotator running and the rotor directly output the speed and torque. During the working course, the lowest steady speed is 0.001 °/s, the highest rotary speed is 100°/s, the position accuracy is ±0.002o, and the largest output torque is 6000 Nm. The servo motor has perfect super low speed, high frequency response, wide speed range, high precision performance, and so on.

This work has been supported by National Defense Basic Research Program and obtained one Chinese invention patents.

    8    Hydraulic Hybrid System Test Bench

        Hydraulic hybrid system test bench is a necessary experimental equipment for theoretical verification, effect test and performance analysis before engineering realization of a hydraulic hybrid system. It can accomplish simulation experiments on the working mechanism, system performance, energy saving effect and control strategies of serial and wheel-drive hydraulic hybrid vehicle as well as other hybrid systems’ experimental research.
        The test bench built by our laboratory is mainly used in research of key techniques in hydraulic hybrid vehicle including braking energy recovery and optimization, hydraulic pump/motor precise control and re- generation braking cooperation with friction braking technique. It can solve key techniques of hybrid system, promoting the system’s extension and application which is very important for energy saving and environment protection.
This work is supported by NNSF and State Key Lab Opening Fund.

The hydraulic system of hybrid full-hydraulic excavator has the characteristics of simple structure, convenient operation, energy conservation and environment protection. Fuel economy, low emissions and low fuel consumption can be achieved because it keeps the engine working in the high efficiency area,. Fitting or refitting hydraulic units can recover energy at actuators such as walking mechanism, slewing mechanism and cylinders on boom, bucket rod and bucket ensures that the system can work under the best energy use condition.
Hydraulic hybrid excavator’s hydraulic system adopts constant pressure variable pump as oil source which forms common pressure rail (CPR), i.e. all the actuators work under the same pressure and they work independently without any interactions. During working cycles, some loads can feedback energy into CPR thus providing other actuators’ working energy or stores energy into the hydraulic accumulator. The peak value of power can be provided by the energy stored in the hydraulic accumulator, so that the system can be designed according to the average power which minimizes the whole system’s installed power. The technique can efficiently solve the problems of existing excavators such as fuel economy and serious pollution.
The researching technique includes: 1) working principle of hydraulic hybrid excavator; 2) configuration of hydraulic hybrid excavator; 3) hydraulic hybrid excavator actuators precise control; 4) energy regeneration under linear and rotating working style.
This research is supported by NNSF and State Key Lab Opening Fund.

    10 Hybrid Hydraulic Power System of Air Plane Tractor

        The design of this hybrid power system in application of air plane tractor has the advantages of: 1) the application of hydrostatic transmission with secondary regulation makes wheel-side hydraulic motor/pump drive wheels through a wheel-side speed reducer. Hydraulic energy storage holds a great power density. Meanwhile, the electro-hydraulic control of hydraulic motor/pump has high accuracy and characteristic of four quadrant work, which can store brake energy in accumulators; 2) hydraulic energy accumulators which are controlled by a switch can provide assistive power and reduce fluctuation of system pressure. This makes driving torque stable. It can also serve as backup-power source on mechanisms and vehicles; 3) make the detachment of engine and vehicle driving load. Stepless speed regulation of this system can adjust operating point of engine between the economy area and the low emission area; 4) reduce usage frequency and intensity of brake, and lower service and maintainence fees; 5) improve riding stability of vehicle and promote driving comfort.
This research is supported by NNSF and State Key Lab Opening Fund.

     11 Direct    Drive    Electro-Hydraulic    Self-Propelled Transporter

    The existing self-propelled transporter has some disadvantages of high fuel consumption, complicated mechanical structure and tube layout. The transporter on which our institute is researching uses the direct drive volume control (DDVC) electro-hydraulic servo system. Variable displacement pump and proportional valve are replaced by a converter motor and bidirectional fixed pump. Changing the rotating direction, rotating speed and runtime of the converter motor can control the moving direction, velocity and position of the hydraulic actuator. The hydraulic steering system combines with the hydraulic driving system. The transporter turns around by means of controlling the relative velocity of the two motors which are equipped in the opposite sides of the driving axle. So, it simplifies the mechanical structure. Replacing pipelines, this system uses cables to connect every hydraulic pocket so that this system is energy saving and has higher reliability and more compact structure. This research is supported by NNSF.

    12 DDVC Material Testing Machine

DDVC electro-hydraulic servo system is a combination of AC servo technology and hydraulic technology. It is a new type of energy-saving servo-control device which has flexible control and high output. In the system, the AC servo motor drives a constant displacement pump, by changing the speed of the servo motor to change the oil output of the pump. The flow direction of the oil is the same as the rotating direction of the AC motor. Then, the system can realize the control of the hydraulic actuator. The DDVC system for material testing machine loading system, which replaces the traditional electro-hydraulic servo valve control system, will play an important role in the promotion of hydraulic material testing machine technology.

13 DDVC pitch-control system of wind generator

The aim of this research is to apply the DDVC servo system into individual blade pitch control system of large wind generators. In this case, we’ll design and produce a new DDVC system, analyze the performance, study efficiency and control strategies of it and make a lot of experiments under the extremely natural conditions on it. We want to replace the valve -control electro-hydraulic pitch-control system with the DDVC system. Compared with servo-motor-drive pitch-control system, the performance and cost of this system are competitive.

    In recent years, we’ve studied and analyzed the inner mechanism, hydraulic circuits and control strategies of the DDVC system. At the same time, we produced two small DDVC systems for a couple of experiments to support our research conclusions. Through 2010, we’ve applied this system into many fields. Now we’re doing several projects concerning DDVC including direct drive volume-control pitch-control system of wind generators, direct drive volume-control yaw system of wind generator, direct drive volume-control braking system of wind generator, and direct drive volume-control hydraulic servo-motor of feed water pump turbine, etc.

        Our institute has built up symbiosis with many large and medium enterprises in China, and some of them have established cooperative laboratories with us such as the HIT–Shanghai Huiyi Cooperation Laboratory, the HIT-Anhui Boyi Cooperation Laboratory, the HIT-Weihai Renhe CEEUSRO Center, etc., which improves our capability of transforming basic research achievements into commodity products.
        We keep connecting with many colleges of China and other countries, such as Beijing Science and Technology University (China), Zhejiang University (China), Linkoping University (Sweden) and Ulsan University (Korea). Through regular academic communication, we broaden our scientific research eyeshot and make some good friends.

        The staff of our institute take the charge of undergraduate and graduate lectures of Hydraulic Transmission, Hydraulic and Pneumatic Transmission, Hydraulic Servo System, Engineering System Modeling and Simulation, etc. at Harbin Institute of Technology and Harbin Huade College of Application Technology. The undergraduate lecture named Hydraulic Transmission has been awarded the prize of Excellent Lecture in Heilongjiang Province in 2009. We have published textbooks of Hydraulic Transmission, Hydraulic and Pneumatic Transmission, network lecture material, multimedia courseware and other teaching materials and monographs, and the total number is 52.
        We have trained and supervised 69 master’s degree students and 58 doctor’s degree students since the institute was founded, many of whom have become the leaders in their working fields.
There are foreign students training stations in our institute. Foreign graduate students who are doing research here can apply for HIT Scholarship from Foreign Student Center of HIT.