Abstract: To satisfy the motility, agility and security of the loader in making truing in
limited domain through the design of its steering system, the common way is through virtual
simulation design. The working characteristic of the loader steering system is firstly analyzed,
including system structure, working principle and system simplify model. Then, the power bond
graph of the steering hydraulic system is constructed through bond graph tool according to energy
and information transformation. Also, the equation of state is deduced by the power bond graph. A
hydraulic steering system simulation model is constructed in MWORKS software, and simulated
steering working process. The completed theory and method of little type multifunctional loader
are offered. It is not only significant in theory, but also very valuable in practice.

Key words: multifunctional loader, power bond graphs, steering hydraulic system, state
equation