How fast does the hydraulic power unit respond?

The response speed of hydraulic power unit is influenced by various factors, and the overall performance is relatively complex, so it cannot be generalized as "fast" or "slow". Specifically, it can be understood from the following aspects:

There is inherent delay (compared to electrical):
The physical properties of oil: Hydraulic oil has viscosity (flow resistance) and a certain compressibility (especially under high pressure). After the pump is started, it takes time to establish pressure, overcome pipeline friction, promote oil flow, and fill the chamber of the actuator (cylinder/motor) before starting to push the load. This process has a significant time lag compared to the transmission of electrical signals and the starting of motors.
System volume effect: The larger the internal volume of the entire system (pipes, valve blocks, cylinder/motor chambers), the more oil needs to be filled, the longer the time required to establish pressure and generate action, and the slower the response.

Valve type is the core influencing factor:
Switching valve (directional valve): This type of valve has only two states: "open" and "closed" (such as an electromagnetic directional valve). The action is relatively direct and fast. Once the valve core is switched in place, the oil flow will be turned on or off, and the load will start or stop. But its speed control is not precise, and the start/stop impact is significant.
Proportional valve/servo valve: This type of valve can accurately and continuously regulate flow and pressure. Although its own response speed can be extremely fast (especially for servo valves), the response speed of the entire closed-loop control system still depends on sensor feedback, controller calculation speed, and actuator load inertia. When pursuing high-precision dynamic control, system design and debugging are crucial, with great potential for response speed but requiring cost and complexity. In contrast, proportional valves typically respond slower than servo valves but faster than regular on/off valves.

The impact of pump control and valve control:
Valve control system (most common): The pump outputs oil at a basic constant speed/flow rate, and the speed and direction of the load are controlled by adjusting the opening of the valve. The switching or adjustment speed of the valve directly determines the speed at which the action begins. The distance from the valve to the actuator (pipeline length) also affects the delay.
Pump control system: Directly change the output flow of the pump (such as using a variable frequency motor or variable displacement pump) to drive the load. Reducing throttling losses and potential delays in the valve control process theoretically allows for faster and more efficient response. But the variable mechanism response speed and closed-loop control complexity of the pump itself are limiting factors.

Characteristics of executing components:
Oil cylinder vs. motor: Hydraulic motors usually respond slightly faster than oil cylinders because oil cylinders need to drive larger pistons and rods to reciprocate, resulting in greater inertia.
Component size: Large displacement cylinders/motors require a larger amount of oil to fill, and their response speed is usually slower than small displacement components.

Load inertia and friction:
The larger the mass (or moment of inertia) of the load itself, the greater the force (or torque) required to accelerate or decelerate it, and the longer it takes, resulting in slow response (especially during start-up and shutdown).
The high frictional resistance of the load can also delay the initiation of initial motion.

The influence of temperature:
The viscosity of hydraulic oil varies significantly with temperature. During cold start (low oil temperature, high viscosity), the oil flow resistance is high, the pressure establishment and oil filling are slow, and the response speed significantly deteriorates. After the system reaches normal operating temperature, the response speed tends to stabilize.

System design and optimization:
Reasonable pipeline layout (as short as possible, with appropriate pipe diameter), reducing unnecessary chambers, selecting valves with fast response speed (such as high-frequency proportional valves or servo valves), and optimizing control algorithms (closed-loop control) can significantly improve the response speed of the system. On the contrary, poorly designed systems will respond more slowly.