The lifting mechanism includes a battery, an electric machine, a hydraulic pump, an oil tank, a hydraulic cylinder, a work platform and a proportional valve or switch valve. In the energy-regeneration mode, the hydraulic fluid drives the hydraulic pump to operate as a hydraulic motor, thus in turn driving the electric machine to operate as a generator and charge the battery. In the present application, the hydraulic pump operates to increase a pressure in a hydraulic line between the hydraulic pump and the proportional valve or switch valve before the proportional valve or switch valve is switched from a unidirectional communication position to a bidirectional communication position. When the proportional valve or switch valve is switched from the unidirectional communication position to the bidirectional communication position, by increasing the pressure in the hydraulic line, it could be avoided that the volume of hydraulic fluid has low pressure is compressed because the hydraulic fluid has low pressure is communicated with hydraulic fluid has high pressure; therefore a state of sudden drop of the work platform is avoided, and safety performance and operating experience of the lifting mechanism is improved.

An engine oil system includes a filter assembly, a sensor assembly, and a controller. The filter assembly includes a filter and a bypass valve. The filter assembly forms a portion of an oil flow path of the engine oil system. The sensor assembly includes an inlet pressure sensor, an outlet pressure sensor, and a temperature sensor. The controller is configured to control a position of the bypass valve in the open position or the closed position with an unfaulted control routine using a temperature (T.sub.OIL) measured by the temperature sensor and a differential pressure (P.sub.OIL) measured by the inlet pressure sensor and the outlet pressure sensor, execute a bypass valve control algorithm configured to identify a faulted condition and an unfaulted condition of the sensor assembly, and identify the faulted condition or the unfaulted condition using the bypass valve control algorithm. The faulted condition is identified where the temperature (T.sub.OIL) or the differential pressure (P.sub.OIL) is outside of an expected temperature range or an expected differential pressure range, respectively.

A hydraulic drive includes a hydraulic pump that discharges a working fluid; a travel system hydraulic circuit that is connected to a first passage branching from a pump passage connected to the hydraulic pump and controls a flow of the working fluid to a travel motor; a loading system hydraulic circuit that is connected to a second passage branching from the pump passage and controls a flow of the working fluid to a loading actuator; a flow rate control valve that is interposed in the second passage and changes an opening degree of the second passage according to a signal; a travel-end pressure sensor that detects a pressure being supplied to the travel motor; and a control device that controls, by outputting the signal to the flow rate control valve, the opening degree of the second passage according to the pressure detected by the travel-end pressure sensor.

An engine oil system includes a filter assembly, a sensor assembly, and a controller. The filter assembly includes a filter and a bypass valve. The filter assembly forms a portion of an oil flow path of the engine oil system. The sensor assembly includes an inlet pressure sensor, an outlet pressure sensor, and a temperature sensor. The controller is configured to control a position of the bypass valve in the open position or the closed position with an unfaulted control routine using a temperature (T.sub.OIL) measured by the temperature sensor and a differential pressure (P.sub.OIL) measured by the inlet pressure sensor and the outlet pressure sensor, execute a bypass valve control algorithm configured to identify a faulted condition and an unfaulted condition of the sensor assembly, and identify the faulted condition or the unfaulted condition using the bypass valve control algorithm. The faulted condition is identified where the temperature (T.sub.OIL) or the differential pressure (P.sub.OIL) is outside of an expected temperature range or an expected differential pressure range, respectively.

A lifting mechanism has a descending mode including an energy-regeneration mode and a non-energy-regeneration mode. The lifting mechanism includes: a battery, an electric machine, a hydraulic pump, an oil tank, a hydraulic cylinder, a work platform and a flow limiting valve. In the energy-regeneration mode, the hydraulic fluid drives the hydraulic pump to operate as a hydraulic motor, thus in turn driving the electric machine to operate as a generator and charge the battery. In the non-energy-regeneration mode, the flow limiting valve limits the maximum of the descending speed of the work platform. In the present application, the flow limiting valve is used to provide throttling resistance to limit the maximum of the descending speed of the hydraulic fluid, thus in turn defining the maximum of the descending speed of the work platform. Therefore, in the present application, by using the flow limiting valve to define the maximum of the descending speed of the work platform, the safety problem due to an accelerated descent during descending of the work platform may be solved, and thus the safety of the lifting mechanism may be ensured.