Appropriate technology for India

Illustration | Bosch Rexroth AG
Marginal Column

Sales engineer and production engineer discuss components for EHC-8

Discussion of EHC-8 system components within the development department

When introducing the EHC-8 Electrohydraulic Hitch Control to the Indian market, engineers initially made preparations without taking account of the adverse environmental conditions. Project managers Raman Sheshadri and Uwe Falkenhain report on how adaptation to local circumstances resulted in a genuine success.


Bosch Rexroth has had excellent results with the Electrohydraulic Hitch Control in both the European and North American markets. Farmers fully appreciate the advantages it offers. Precise regulation of power and position makes for exact lifting and lowering the hitch and, as a result, highly accurate tillage.

Soils are turned over gently and uniformly. That improves yields. And the work is more convenient, as well. That is why, in 2009, we decided to introduce Electrohydraulic Hitch Control (EHC) on the Indian subcontinent – an equipment market with enormous potentials. But the feedback from initial test runs using tractors built by local manufacturers was not entirely satisfactory. We did see a need for this concept, but it had to be more rugged and considerably less expensive.

Adapting and new development

When reworking the system for the Indian market, our first step was to conduct a closer analysis of the operating conditions. The tractors have to survive the most foreboding conditions: monsoons, high relative humidity on the one hand, and dryness, dust and heat on the other hand. All this is aggravated by the demands made in rice cultivation.

Here the parts are sometimes submerged in centimeters of packed-down mud. What’s more, the tractors usually have no sprung suspension and, as a result, generate greater vibration. In order to cope with these operating parameters and, at the same time, to drastically cut the costs for the system, we decided simply to modify certain components and to develop others from scratch.

Brand new: Control panel and angular sensor

Two components in particular are exposed to the extreme weather conditions: the angular sensor and the control panel. Our standard control panel, designed for installation inside the operator’s cab, was not suitable for use in Indian tractors without a protective cab. That is why we needed something entirely new. Not only did it have to be more rugged. The illumination needed to be brighter since – given the intense sunlight – it was impossible to see the operating functions.

Placement was yet another question. Following extensive deliberation, the customer and we agreed to engineer an armrest ready to accept the control panel. This steadies the farmer’s hand when he presses the various buttons. We replaced the large actuator lever with a generously dimensioned switch with three positions: lift, lower, off.

The components of the EHC-8 system

The components of the EHC-8 system. The entirely redesigned control unit is at the upper right.


Another very important item was to offer farmers a service concept. Local workshops are normally unable to read out the electronic fault diagnosis. That is why we integrated that function into the control panel, with a display to output the results. Now the farmer can himself determine whether an electronic component is malfunctioning. To protect the entire control panel – and above all the display – we have fitted the unit with a sturdy film to keep out moisture and dust and to reduce mechanical influences.

In questions of resistance to leaks, we had to depart from European thinking. The IP 67 protection class used for the angular sensor in Europe is not sufficient to withstand the extremely dusty conditions. As a consequence, we had to entirely re-engineer the sensor. The electrical components are now completely separate from the mechanical space.

Indian software relationships

We also developed the controller from the ground up. It is installed in the housing Bosch had designed for the Tata “Nano” city car. That housing is already laid out to handle the Indian climate. The software had to be adapted to the Indian market as well – shifting from the European lower linkage control to upper linkage control. This requires only one power regulation sensor instead of two and helps us reduce costs.

Drawing upon local resources

To achieve a more attractive price for the Indian design, we turned to local suppliers who manufacture in India. Thus we established local production capacities for the EHR5 valve. This valve regulates the flow of hydraulic fluid to the cylinders, lending precision to raising and lowering the lifting unit.

On the other hand, we have done away with many complex, automated procedures. One good example is the rear cover for the angular sensor. In our standard designs, ultrasonic welding is used. In principle, this would be possible in India, but we decided to use an appropriate adhesive, which is far less costly.

Engineering for cost savings

Design options offered a further way to reduce costs. The selection of the materials is one example. The plastics found on the Indian market are far different from those in Europe. Their strength is aligned exactly with the conditions and they are less expensive, as well. Glass fiber reinforcement is seldom used, for example.

In addition, we eliminated a large number of parts. In the European version of the angular sensor, there is a component that lets us program the sensor for various ranges of angles, depending on the geometry of the lifting system. We have done away with this in the Indian version and regulate the opening angle using a resistor, which is soldered in place.

Our research into the potentials for cost reductions will not end when our Indian customer launches mass production in the first quarter of 2014. At present, we are working intensively on replacing the existing power measurement sensor with a newly developed system tailored exactly to the power ranges used in India. We will be able to achieve savings on the one hand by converting from a magnetic-elastic measurement principle to a Hall effect sensor. In addition, we can have this draft pin sensor manufactured locally, in India.

Larger than India

Customizing the system has already paid off – beyond the Indian market. This readies us for taking the next step in other BRIC nations, where similar conditions prevail. In addition, individual components will also be of interest to European customers who can then integrate them into their overall concepts.



Raman Sheshadri,

Sales and Industry Sector Management, Agricultural and Forestry Machinery,

Bangalore, India

Uwe Falkenhain,

Sales and Product Management Mobile Electronics,

Schwieberdingen, Germany